I will examine the concept of chirality (the difference between a right hand and a left hand, generalized) and its relevance to philosophy of mind. Philosophy of mind often deals with colors: colors of worldly objects and of mental representations of them. Chirality, like color, can be experienced: it feels different to look at a left hand compared with looking at a right hand. Physics treats chirality more directly than it treats color.
Parity symmetry is a feature of some physical universes, but not our own. A parity symmetric universe (assuming it is, like ours, 3D in spatial coordinates) has the property that a universal parity inversion (which negates x, y, z coordinates of everything) makes no physically detectable difference. Parity symmetry is broken in our universe; this was shown in 1957. As a science fiction exercise, I imagine a universe much like ours, but with parity symmetry.
In another universe...
In this parity-symmetric universe, physicists fail to detect any parity violation, concluding that parity symmetry really does hold. They conclude that a possible cosmic state of affairs, and its parity inversion, are physically equal. There is no physical difference between them, only a change in coordinates. The universe needs no absolute chirality, any more than it needs absolute spatial coordinates: chirality is not an intrinsic physical feature of objects.
Philosophical attitudes differ. Physicalists believe the physicists' parity-invariant ontology is correct: absolute chirality exists neither in objects, nor in mental perceptions. This ontology is counter-intuitive, because the experience of looking at a normal clock seems different from the experience of looking at a backwards clock.
Chiral materialists believe that physicists have left something out of their description of the universe. They believe that objects really do have absolute chiral properties: a forwards clock is intrinsically different from a backwards clock. Chiral materialists hold that, while chirality is not strictly speaking a physical property, it is a material property of objects, and not an intrinsically mental one. Chiral materialists are attracted to a Newtonian or 3D cellular-automaton picture of the universe, in which chirality really exists at the fundamental level, even if physicists cannot detect it.
Chiral materialists disagree about how human perception of chirality works. Direct realists say that humans directly perceive the material chirality of objects they look at, at least in the good case of veridical perception. Indirect realists say that humans create internal mental replicas of objects, and then directly perceive the (material) chirality of these replicas.
In cases of veridical chirality perception, there is not a good way to tell the difference: any internal replica of the object would have the same chirality as the object itself. But hallucination is, in principle, possible. A human could look at a normal clock, and by physical miracle, receive a retinal image as if looking at a left/right flip of that clock. Indirect realists reason that the human's internal replica of the clock now has reversed chirality, and the human perceives this replica, which is why they see the clock as backwards. Direct realists say this is a case of false perceptual belief, and should not be taken too seriously as ontology.
Direct and indirect realist chiral materialists agree that, if there is a planet out there that is an exact chiral inverse of Earth, then reverse-chiral humans are having chirality-reversed experiences. Both the material objects they look at, and any internal replicas (if those exist), have reverse chirality. The reverse-chiral humans' veridical perception of what they would consider a normal clock is, according to humans, a backwards clock.
Chiral dualists point out an "epistemic gap" for chiral materialism. Even granting that material objects (and any internal replicas of them) have intrinsic chiral features, why must phenomenal experiences of them take on the chirality of the objects or the replicas of them in the brain? Chiral dualists argue that a "phenomenal chiral invert" is conceivable: someone could be physically (and material-chirally) identical with a normal human, yet have a consistent left/right mirroring in their entire experience (visual, auditory, tactile, and so on). Their visual experience of seeing a normal clock is like a typical person's visual experience of seeing a left/right inverted clock; they're just used to it, so they act normal about it.
Chiral materialism gives no easy way of ruling out this scenario; it's really a guess that experiences track the material chirality of external or internal objects. Chiral dualists infer, from the conceivability of chiral inverts, that there must be a non-material feature which fixes chirality. Perhaps humans have souls, which contain Euclidean world models, and these models generally agree with the physical aspects of their perception.
Chiral idealists argue that chiral dualists' picture is inelegant. While people feel like they are separate from each other, it is possible to consider that "group minds" might exist, spanning multiple humans, and that this group mind could experience chirality. And a region of the human brain could be its own subject experiencing chirality. Chiral dualists need to believe in strong subject boundaries so that phenomenal chirality can flip on a per-subject basis. Instead, chiral idealists suppose, like chiral materialists, that objects have intrinsic chiral properties, but unlike chiral materialists, they consider the object to be entirely an idea in the mind of God, who dissociates into multiple apparent subjects (like human subjects). When chiral idealists imagine a "chiral invert", they most easily imagine that this invert lives in an entirely chirally-inverted universe, not that only their soul is chirally inverted.
Chiral Russellian monists present a middle path between chiral materialism and chiral idealism. They believe that physics gives the chirally-invariant structure and dynamics of the universe, but leaves out the intrinsic nature of objects. That intrinsic nature, they say, includes chirality, neutral between mental and physical, and un-detectable by physics. Chiral Russellian monists agree with indirect realists that phenomenal consciousness is influenced by intrinsic chiral features of the brain, but attribute mental or proto-mental aspects to such features instead of purely material ones.
Chiral physicalists believe that physics (which quotients over parity) gives the complete fundamental ontology, and attempt to reconcile this ontology with chiral experience in one way or another. Chiral reductionists believe that chiral concepts can be analyzed into physical concepts (which are non-chiral), contra chiral dualists' claim that chirality inversion is conceivable. However, they run into trouble giving a convincing reductive definition.
Advocates of the chiral concept strategy (CCS) take a sophisticated approach. They divide concepts into chirally-invariant concepts (such as those of algebra) and chirally-variant ones (such as those of constructive geometry). They claim, contra chiral reductionists, that chirally-variant concepts cannot be defined in terms of chirally-invariant concepts, because chiral inversions change chiral-variant properties but not chiral-invariant ones. However, CCS theorists disagree with chiral dualists: they believe this failure of conceptual reduction implies no ontological gap. CCS theorists believe that chiral-variant concepts can still co-refer with physical concepts, even if physicalism is true. This co-reference must be a posteriori, as no decisive logical inference from the chirally-invariant concepts of fundamental physics to chiral-variant concepts is possible.
CCS theorists point to research of "neural correlates of chirality" (NCCs). When human subjects see normal clocks, they have different neural firing patterns than when they see left-right inverted clocks. Notably, these firing patterns are not chiral inverses of each other: they differ physically, not just chirally. This suggests empirical evidence in favor of an posteriori identity: maybe normal-clock neural firing patterns are experiences of normal clocks, even though this connection is non-analytic.
CCS proponents disagree with chiral materialists. First, CCS proponents believe physicalism is likely, implying that nothing has absolute chirality. Second, CCS proponents believe that reverse-chiral humans would have the same experiences, because their neural correlates of chirality (NCC) are the same, up to a parity inversion (which, they emphasize, makes no physical difference).
Critics, especially chiral dualists and idealists, argue that CCS mis-characterizes chiral concepts. Since NCCs are characterized in chiral-invariant neuroscientific language, it is highly counterintuitive, if not contradictory, to claim an identity with experiential chirality, even an a posteriori one. This identity would require a lack of conceptual transparency in chiral-variant concepts (such as those of constructive geometry, and mental Euclidean imagination): that users of these concepts fail to grasp the nature of the properties the concepts refer to. But Euclidean geometry, with all its chiral-variance, is as intuitive as can be: why expect concept users to be ignorant as to the nature of the properties referred to by these concepts?
Chiral illusionists agree with CCS proponents that chiral concepts cannot be analyzed into chiral-invariant concepts, and agree with non-physicalist critics that chiral concepts are really supposed to be referring to something chirally variant, not anything physical (therefore chirally-invariant). Chiral illusionists hold that physicalism is nonetheless true, and that accordingly, chiral-variant concepts do not refer. Chiral illusionists believe that chirality, both the chirality of external objects and of internal experiences, is an illusion, which can be "debunked" by explaining the appearance of chirality using chirally-invariant language. As long as the illusionist can predict people's chirally-invariant reports about their so-called "chiral experiences", they believe they have an adequate model, and positing "true chirality" is unnecessary.
This idea seems crazy and incoherent to many. Isn't it obvious that experiences have chiral properties? That right hands have a way they look, and left hands have a different way they look? If the chirality is, as physicists say, not in the object itself, it has to be in the mind: where else could it be? CCS advocates say that chiral illusionism goes too far, and that physicalism can be reconciled with the reality of chiral experience.
Chiral reductionists point out that CCS theorists could be over-estimating the epistemic gap between physical and chiral concepts. In particular, to the degree reference is physical, physics is enough to decode the meanings chiral concepts; and the empirical evidence of NCCs and the plausibility of a posteriori identities suggests, on many accounts of meaning, that such connections exist, and could be unpacked by Laplace's demon, if not by actual humans.
Comparison with color quality
Philosophers of mind discuss color much more than they discuss chirality. Some of the lessons translate, though there are notable differences. In the parity-symmetric universe, chirality is close to a real fundamental physical feature of objects, but doesn't quite make it. Color is further from being a fundamental physical feature. In particular, "color materialism" as an analogue of "chiral materialism" would be implausible as a physical theory: objects are not really painted with colors that are further facts on top of their quantitative physical features like reflectance patterns.
Direct realism about color says that objects really have color qualities, as perception presents them as having. Indirect realism about color says that color is "in the mind": mental pictures of the external world have color quality, or "qualia". The brain itself is not correspondingly colored like these apparent mental pictures (it's dark inside, and looks pink when illuminated), so it's not obvious how to locate color qualia.
The "inverted qualia" thought experiment is famous: many philosophers believe that it is conceivable that someone could behave identically to a normal person (and even be physically identical) while having a red/blue inversion in their color qualia. This conceivability claim is deployed in favor of non-physicalism about color (e.g. property dualism). The "inverted chirality" thought experiment is similar; I don't see a good reason why the conceivability of color inverts would differ from the conceivability of chiral inverts.
With both chirality and color, dualism has problems with subject boundaries: if two humans start sending neural messages to each other (through some medically-innovative neural connection between their brains), and one human is a color invert, do the color qualia invert when traveling across the boundary? Similar questions arise for "group minds" and sub-personal minds. Idealism presents a more color-coordinated image of the universe, where color qualia really exist and are in principle comparable between different humans, e.g. because all qualia are in the mind of God. Russellian monism (especially panpsychism) has some resonance with idealism, but scales back the theology towards a "physicalism + intrinsic natures" ontology. It retains the idea that the qualities of color qualia are fundamental to the universe.
Instead of reverse-chiral life, idealists and Russellian monists can imagine a universal color quality inversion (say, red/blue). Russellian monists imagine this by imagining quiddities swapping with each other, while preserving all structural-physical features; idealists might imagine a color swap in the mind of God. Either way, there is some theoretically possible implementation of a color quality swap that makes no physical difference, and is physically undetectable.
Color reductionists (e.g. analytic functionalists) believe that, in principle, terms like "red qualia" have physical definitions, which would be conceptually clear on ideal reflection. However, most philosophers of mind disagree with them: they think a physical definition would miss the mark of the actual "red qualia" concept, deflating it into something weaker.
Type B physicalism generally involves the "phenomenal concept strategy" (PCS, like CCS above), and claims that there are a posteriori co-references between phenomenal concepts (including "red qualia") and physical concepts. In the chirality case, it is easy to see, at the mathematical level, why the chiral-variant language of constructive geometry is irreducible to the chiral-invariant language of algebra. PCS claims, analogously, that color qualia concepts are irreducible to physical and functional concepts; that qualities cannot have reductive definitions in the quantitative, mathematical language of fundamental physics. Compare the "language" of visual art to the "language" of theoretical physics. Nevertheless, a posteriori identities are plausible.
While color qualities per se are not really out there painted on objects, it is possible to maintain that external color is a certain light reflectance pattern (say, ~700nm wavelength for red), and that this identity is a posteriori, like "water is H2O". Brain-internal a posteriori identities might be plausible based on investigating neural correlates of consciousness, and in particular, neural correlates of color experience. Identity would explain why red qualia appear whenever their neural correlates occur. This may lead to some a posteriori identity of the classic "pain = C-fiber firing" sort for color qualia, perhaps in terms of the neurology of the visual cortex.
As with chirality, the neural correlates approach disagrees with idealists and Russellian monists about "universal color inversion". Idealists and Russellian monists hold that universal color quality inversion (e.g. by a quiddity swap) would make a difference to human color qualia, yet no neural correlate would change (as nothing would physically change). Type B physicalists would disagree, holding that even if fundamental qualities exist, quality swaps that make no physical difference do not change humans' color qualia. This is in line with the type B conclusion that reverse-chiral life has identical experiences (in a parity-symmetric universe).
Non-physicalists object to type B physicalism and PCS on various bases. Philip Goff's "transparency" and "revelation" critiques are popular, which claim that PCS's a posteriori identities are incompatible with the commonly-held intuitions that phenomenal concepts (e.g. that of "red qualia") reveal the nature of what properties they refer to, are easily mastered by their users, and are not opaque. This is analogous to the intuitive mastery of Euclidean geometry and its implied chirality (Kant claimed that Euclidean geometry is synthetic a priori). Type B physicalists hold that the "red qualia" concept fails to disclose the a posteriori identity with a neural structure, contra transparency and revelation.
Illusionism about color qualia states, simply, that color qualities exist neither out in the world nor in the head, nor in any non-physical "phenomenal realm". The basic idea is that there is a common improper reification in the idea of "color qualia", and that the concept actively misrepresents the situation (by attributing primitive qualities that do not really exist), rather than just being opaque, as the type B physicalist claims.
Conclusion
As for my own views, I believe that in a parity-symmetric universe, reversal-chiral life does not feel any different. This claim is suggested by the neural correlates approach, and it remains likely even if chirality is a real material property, as it would be an undetectable material property. Type B physicalism about chirality therefore seems more likely than dualism, idealism, or Russellian monism about chirality.
I think the color case is reasonably analogous. Even if there are fundamental qualities to the universe ("quiddities"), it seems more reasonable to identify color experiences with neural correlates or functional states than with anything quiddity-level. This is analogous to an a posteriori identity between the colors of external objects and the objects' wavelength reflectance patterns. Advanced neuroscience would predictably find neural correlates of color experience, making the empirical case for identity clearer.
With chirality, it is easy to make a case for the non-analyzability of chiral-variant concepts into chiral-invariant concepts. With color, the case for non-analyzability is less straightforward. Perhaps certain structural asymmetries about color hold as a consequence of the asymmetry in the human color space, and these asymmetries will yield structural conceptual analyses of color. Such analyses would vindicate analytic functionalism about color qualia. On the other hand, if such structural analysis fails, type B physicalism and illusionism are more plausible forms of physicalism. (The disagreement between type B physicalism and illusionism is mostly about how phenomenal concepts characterize their supposed referents; positive mis-characterization would suggest illusionism, while opacity would suggest type B physicalism.)
My overall view is that there is no "hard problem of color": scientific understanding of human color perception and color-related phenomenal concepts will yield hard-problem dissolution as a side effect. I am less sure about non-color phenomenal concepts, such as "phenomenal consciousness" (the property that, supposedly, humans have and P-zombies lack). If there are "consciousness qualia" which inform people that they are conscious, they seem significantly more abstract than "red qualia", so it's less clear how to model them. In any case, better understanding of sensory qualia concepts is an important step towards understanding of more abstract consciousness-related concepts.
I will examine the concept of chirality (the difference between a right hand and a left hand, generalized) and its relevance to philosophy of mind. Philosophy of mind often deals with colors: colors of worldly objects and of mental representations of them. Chirality, like color, can be experienced: it feels different to look at a left hand compared with looking at a right hand. Physics treats chirality more directly than it treats color.
Parity symmetry is a feature of some physical universes, but not our own. A parity symmetric universe (assuming it is, like ours, 3D in spatial coordinates) has the property that a universal parity inversion (which negates x, y, z coordinates of everything) makes no physically detectable difference. Parity symmetry is broken in our universe; this was shown in 1957. As a science fiction exercise, I imagine a universe much like ours, but with parity symmetry.
In another universe...
In this parity-symmetric universe, physicists fail to detect any parity violation, concluding that parity symmetry really does hold. They conclude that a possible cosmic state of affairs, and its parity inversion, are physically equal. There is no physical difference between them, only a change in coordinates. The universe needs no absolute chirality, any more than it needs absolute spatial coordinates: chirality is not an intrinsic physical feature of objects.
Philosophical attitudes differ. Physicalists believe the physicists' parity-invariant ontology is correct: absolute chirality exists neither in objects, nor in mental perceptions. This ontology is counter-intuitive, because the experience of looking at a normal clock seems different from the experience of looking at a backwards clock.
Chiral materialists believe that physicists have left something out of their description of the universe. They believe that objects really do have absolute chiral properties: a forwards clock is intrinsically different from a backwards clock. Chiral materialists hold that, while chirality is not strictly speaking a physical property, it is a material property of objects, and not an intrinsically mental one. Chiral materialists are attracted to a Newtonian or 3D cellular-automaton picture of the universe, in which chirality really exists at the fundamental level, even if physicists cannot detect it.
Chiral materialists disagree about how human perception of chirality works. Direct realists say that humans directly perceive the material chirality of objects they look at, at least in the good case of veridical perception. Indirect realists say that humans create internal mental replicas of objects, and then directly perceive the (material) chirality of these replicas.
In cases of veridical chirality perception, there is not a good way to tell the difference: any internal replica of the object would have the same chirality as the object itself. But hallucination is, in principle, possible. A human could look at a normal clock, and by physical miracle, receive a retinal image as if looking at a left/right flip of that clock. Indirect realists reason that the human's internal replica of the clock now has reversed chirality, and the human perceives this replica, which is why they see the clock as backwards. Direct realists say this is a case of false perceptual belief, and should not be taken too seriously as ontology.
Direct and indirect realist chiral materialists agree that, if there is a planet out there that is an exact chiral inverse of Earth, then reverse-chiral humans are having chirality-reversed experiences. Both the material objects they look at, and any internal replicas (if those exist), have reverse chirality. The reverse-chiral humans' veridical perception of what they would consider a normal clock is, according to humans, a backwards clock.
Chiral dualists point out an "epistemic gap" for chiral materialism. Even granting that material objects (and any internal replicas of them) have intrinsic chiral features, why must phenomenal experiences of them take on the chirality of the objects or the replicas of them in the brain? Chiral dualists argue that a "phenomenal chiral invert" is conceivable: someone could be physically (and material-chirally) identical with a normal human, yet have a consistent left/right mirroring in their entire experience (visual, auditory, tactile, and so on). Their visual experience of seeing a normal clock is like a typical person's visual experience of seeing a left/right inverted clock; they're just used to it, so they act normal about it.
Chiral materialism gives no easy way of ruling out this scenario; it's really a guess that experiences track the material chirality of external or internal objects. Chiral dualists infer, from the conceivability of chiral inverts, that there must be a non-material feature which fixes chirality. Perhaps humans have souls, which contain Euclidean world models, and these models generally agree with the physical aspects of their perception.
Chiral idealists argue that chiral dualists' picture is inelegant. While people feel like they are separate from each other, it is possible to consider that "group minds" might exist, spanning multiple humans, and that this group mind could experience chirality. And a region of the human brain could be its own subject experiencing chirality. Chiral dualists need to believe in strong subject boundaries so that phenomenal chirality can flip on a per-subject basis. Instead, chiral idealists suppose, like chiral materialists, that objects have intrinsic chiral properties, but unlike chiral materialists, they consider the object to be entirely an idea in the mind of God, who dissociates into multiple apparent subjects (like human subjects). When chiral idealists imagine a "chiral invert", they most easily imagine that this invert lives in an entirely chirally-inverted universe, not that only their soul is chirally inverted.
Chiral Russellian monists present a middle path between chiral materialism and chiral idealism. They believe that physics gives the chirally-invariant structure and dynamics of the universe, but leaves out the intrinsic nature of objects. That intrinsic nature, they say, includes chirality, neutral between mental and physical, and un-detectable by physics. Chiral Russellian monists agree with indirect realists that phenomenal consciousness is influenced by intrinsic chiral features of the brain, but attribute mental or proto-mental aspects to such features instead of purely material ones.
Chiral physicalists believe that physics (which quotients over parity) gives the complete fundamental ontology, and attempt to reconcile this ontology with chiral experience in one way or another. Chiral reductionists believe that chiral concepts can be analyzed into physical concepts (which are non-chiral), contra chiral dualists' claim that chirality inversion is conceivable. However, they run into trouble giving a convincing reductive definition.
Advocates of the chiral concept strategy (CCS) take a sophisticated approach. They divide concepts into chirally-invariant concepts (such as those of algebra) and chirally-variant ones (such as those of constructive geometry). They claim, contra chiral reductionists, that chirally-variant concepts cannot be defined in terms of chirally-invariant concepts, because chiral inversions change chiral-variant properties but not chiral-invariant ones. However, CCS theorists disagree with chiral dualists: they believe this failure of conceptual reduction implies no ontological gap. CCS theorists believe that chiral-variant concepts can still co-refer with physical concepts, even if physicalism is true. This co-reference must be a posteriori, as no decisive logical inference from the chirally-invariant concepts of fundamental physics to chiral-variant concepts is possible.
CCS theorists point to research of "neural correlates of chirality" (NCCs). When human subjects see normal clocks, they have different neural firing patterns than when they see left-right inverted clocks. Notably, these firing patterns are not chiral inverses of each other: they differ physically, not just chirally. This suggests empirical evidence in favor of an posteriori identity: maybe normal-clock neural firing patterns are experiences of normal clocks, even though this connection is non-analytic.
CCS proponents disagree with chiral materialists. First, CCS proponents believe physicalism is likely, implying that nothing has absolute chirality. Second, CCS proponents believe that reverse-chiral humans would have the same experiences, because their neural correlates of chirality (NCC) are the same, up to a parity inversion (which, they emphasize, makes no physical difference).
Critics, especially chiral dualists and idealists, argue that CCS mis-characterizes chiral concepts. Since NCCs are characterized in chiral-invariant neuroscientific language, it is highly counterintuitive, if not contradictory, to claim an identity with experiential chirality, even an a posteriori one. This identity would require a lack of conceptual transparency in chiral-variant concepts (such as those of constructive geometry, and mental Euclidean imagination): that users of these concepts fail to grasp the nature of the properties the concepts refer to. But Euclidean geometry, with all its chiral-variance, is as intuitive as can be: why expect concept users to be ignorant as to the nature of the properties referred to by these concepts?
Chiral illusionists agree with CCS proponents that chiral concepts cannot be analyzed into chiral-invariant concepts, and agree with non-physicalist critics that chiral concepts are really supposed to be referring to something chirally variant, not anything physical (therefore chirally-invariant). Chiral illusionists hold that physicalism is nonetheless true, and that accordingly, chiral-variant concepts do not refer. Chiral illusionists believe that chirality, both the chirality of external objects and of internal experiences, is an illusion, which can be "debunked" by explaining the appearance of chirality using chirally-invariant language. As long as the illusionist can predict people's chirally-invariant reports about their so-called "chiral experiences", they believe they have an adequate model, and positing "true chirality" is unnecessary.
This idea seems crazy and incoherent to many. Isn't it obvious that experiences have chiral properties? That right hands have a way they look, and left hands have a different way they look? If the chirality is, as physicists say, not in the object itself, it has to be in the mind: where else could it be? CCS advocates say that chiral illusionism goes too far, and that physicalism can be reconciled with the reality of chiral experience.
Chiral reductionists point out that CCS theorists could be over-estimating the epistemic gap between physical and chiral concepts. In particular, to the degree reference is physical, physics is enough to decode the meanings chiral concepts; and the empirical evidence of NCCs and the plausibility of a posteriori identities suggests, on many accounts of meaning, that such connections exist, and could be unpacked by Laplace's demon, if not by actual humans.
Comparison with color quality
Philosophers of mind discuss color much more than they discuss chirality. Some of the lessons translate, though there are notable differences. In the parity-symmetric universe, chirality is close to a real fundamental physical feature of objects, but doesn't quite make it. Color is further from being a fundamental physical feature. In particular, "color materialism" as an analogue of "chiral materialism" would be implausible as a physical theory: objects are not really painted with colors that are further facts on top of their quantitative physical features like reflectance patterns.
Direct realism about color says that objects really have color qualities, as perception presents them as having. Indirect realism about color says that color is "in the mind": mental pictures of the external world have color quality, or "qualia". The brain itself is not correspondingly colored like these apparent mental pictures (it's dark inside, and looks pink when illuminated), so it's not obvious how to locate color qualia.
The "inverted qualia" thought experiment is famous: many philosophers believe that it is conceivable that someone could behave identically to a normal person (and even be physically identical) while having a red/blue inversion in their color qualia. This conceivability claim is deployed in favor of non-physicalism about color (e.g. property dualism). The "inverted chirality" thought experiment is similar; I don't see a good reason why the conceivability of color inverts would differ from the conceivability of chiral inverts.
With both chirality and color, dualism has problems with subject boundaries: if two humans start sending neural messages to each other (through some medically-innovative neural connection between their brains), and one human is a color invert, do the color qualia invert when traveling across the boundary? Similar questions arise for "group minds" and sub-personal minds. Idealism presents a more color-coordinated image of the universe, where color qualia really exist and are in principle comparable between different humans, e.g. because all qualia are in the mind of God. Russellian monism (especially panpsychism) has some resonance with idealism, but scales back the theology towards a "physicalism + intrinsic natures" ontology. It retains the idea that the qualities of color qualia are fundamental to the universe.
Instead of reverse-chiral life, idealists and Russellian monists can imagine a universal color quality inversion (say, red/blue). Russellian monists imagine this by imagining quiddities swapping with each other, while preserving all structural-physical features; idealists might imagine a color swap in the mind of God. Either way, there is some theoretically possible implementation of a color quality swap that makes no physical difference, and is physically undetectable.
Color reductionists (e.g. analytic functionalists) believe that, in principle, terms like "red qualia" have physical definitions, which would be conceptually clear on ideal reflection. However, most philosophers of mind disagree with them: they think a physical definition would miss the mark of the actual "red qualia" concept, deflating it into something weaker.
Type B physicalism generally involves the "phenomenal concept strategy" (PCS, like CCS above), and claims that there are a posteriori co-references between phenomenal concepts (including "red qualia") and physical concepts. In the chirality case, it is easy to see, at the mathematical level, why the chiral-variant language of constructive geometry is irreducible to the chiral-invariant language of algebra. PCS claims, analogously, that color qualia concepts are irreducible to physical and functional concepts; that qualities cannot have reductive definitions in the quantitative, mathematical language of fundamental physics. Compare the "language" of visual art to the "language" of theoretical physics. Nevertheless, a posteriori identities are plausible.
While color qualities per se are not really out there painted on objects, it is possible to maintain that external color is a certain light reflectance pattern (say, ~700nm wavelength for red), and that this identity is a posteriori, like "water is H2O". Brain-internal a posteriori identities might be plausible based on investigating neural correlates of consciousness, and in particular, neural correlates of color experience. Identity would explain why red qualia appear whenever their neural correlates occur. This may lead to some a posteriori identity of the classic "pain = C-fiber firing" sort for color qualia, perhaps in terms of the neurology of the visual cortex.
As with chirality, the neural correlates approach disagrees with idealists and Russellian monists about "universal color inversion". Idealists and Russellian monists hold that universal color quality inversion (e.g. by a quiddity swap) would make a difference to human color qualia, yet no neural correlate would change (as nothing would physically change). Type B physicalists would disagree, holding that even if fundamental qualities exist, quality swaps that make no physical difference do not change humans' color qualia. This is in line with the type B conclusion that reverse-chiral life has identical experiences (in a parity-symmetric universe).
Non-physicalists object to type B physicalism and PCS on various bases. Philip Goff's "transparency" and "revelation" critiques are popular, which claim that PCS's a posteriori identities are incompatible with the commonly-held intuitions that phenomenal concepts (e.g. that of "red qualia") reveal the nature of what properties they refer to, are easily mastered by their users, and are not opaque. This is analogous to the intuitive mastery of Euclidean geometry and its implied chirality (Kant claimed that Euclidean geometry is synthetic a priori). Type B physicalists hold that the "red qualia" concept fails to disclose the a posteriori identity with a neural structure, contra transparency and revelation.
Illusionism about color qualia states, simply, that color qualities exist neither out in the world nor in the head, nor in any non-physical "phenomenal realm". The basic idea is that there is a common improper reification in the idea of "color qualia", and that the concept actively misrepresents the situation (by attributing primitive qualities that do not really exist), rather than just being opaque, as the type B physicalist claims.
Conclusion
As for my own views, I believe that in a parity-symmetric universe, reversal-chiral life does not feel any different. This claim is suggested by the neural correlates approach, and it remains likely even if chirality is a real material property, as it would be an undetectable material property. Type B physicalism about chirality therefore seems more likely than dualism, idealism, or Russellian monism about chirality.
I think the color case is reasonably analogous. Even if there are fundamental qualities to the universe ("quiddities"), it seems more reasonable to identify color experiences with neural correlates or functional states than with anything quiddity-level. This is analogous to an a posteriori identity between the colors of external objects and the objects' wavelength reflectance patterns. Advanced neuroscience would predictably find neural correlates of color experience, making the empirical case for identity clearer.
With chirality, it is easy to make a case for the non-analyzability of chiral-variant concepts into chiral-invariant concepts. With color, the case for non-analyzability is less straightforward. Perhaps certain structural asymmetries about color hold as a consequence of the asymmetry in the human color space, and these asymmetries will yield structural conceptual analyses of color. Such analyses would vindicate analytic functionalism about color qualia. On the other hand, if such structural analysis fails, type B physicalism and illusionism are more plausible forms of physicalism. (The disagreement between type B physicalism and illusionism is mostly about how phenomenal concepts characterize their supposed referents; positive mis-characterization would suggest illusionism, while opacity would suggest type B physicalism.)
My overall view is that there is no "hard problem of color": scientific understanding of human color perception and color-related phenomenal concepts will yield hard-problem dissolution as a side effect. I am less sure about non-color phenomenal concepts, such as "phenomenal consciousness" (the property that, supposedly, humans have and P-zombies lack). If there are "consciousness qualia" which inform people that they are conscious, they seem significantly more abstract than "red qualia", so it's less clear how to model them. In any case, better understanding of sensory qualia concepts is an important step towards understanding of more abstract consciousness-related concepts.