You could use a monospace font, the same way that Douglas Hofstaedter distinguishes strings of a formal system in Godel, Escher, Bach. It's poetically appropriate because Hofstaedter was trying to solve the same problem you are: use typesetting to set apart map and territory.
I personally find colors to be distracting and nonstandard ways of carrying such information. I like Samuel Marks's idea of using monospace fonts for strings or formalizations as opposed to concepts. I also VERY MUCH prefer talking about strings vs concepts than map vs territory, as the territory isn't actually available in any text, only different levels of map (in this kind of document; there are other conversations where it makes perfect sense to use map/territory).
Depending on the topic and text, you might also consider physical separation rather than typography as the differentiator. A column for one level of narrative, alongside another column for a different (more objective) level of description. Or more humorously, an OOC injection between paragraphs like
Narrator: Dagon thinks self-reference is fun. Not everyone agrees.
But even more than any specific, I'd love to see some experimentation. Write a sample paragraph, and try out the 3-4 leading styles. If you're into it, write a preprocessor that generates multiple styles from the same input, and let readers choose their preference.
If you ever want to do anything particularly weird in an article, you can send me plain HTML via the Intercom and I insert it into the post directly (after doing some basic sanitization). This will make the post usually admin-only editable (if you used any HTML features that are admin only), but works well-enough, and I've done this a few times for articles that really wanted to use color (Beth's AI Safety Debate writeup was one that comes to mind here)
(Edited for correctness)
There are other plain-text options you might consider.
My first thought (just upon reading the title) was to use the green hyperlink as one color, but that sounds clunkier than using bold or italics, so I'm not sure it's the best way to go. I would find the bicolor notation very helpful, fwiw, but I'm not colorblind and I don't use a screen reader, so I have no input there (and no idea how a screen reader would process a hyperlink).
I am planning to write an article that would use two colors to distinguish between "map" and "territory", kinda like in The Neverending Story. In other words, instead of:
I want to write something like:
In general, the quote marks have the advantage of unlimited nesting, but I don't need it now; my article will have exactly two levels, not more. On the other hand, I feel that the bicolor version may be easier to perceive instinctively; the words referring to the map and the territory are not only surrounded by marks, they look differently by themselves. Also, quote marks are generally used for various purposes (quoting, irony, etc.), so authors emphasise the "this refers to map, as opposed to the territory" usage by not saying merely "X", but "the sentence X", "the words X", "the text X", etc. By removing such words, even my example here is shorter.
So, how to do this technically?
Is there another option I missed here?
Which option would you prefer? I care about everyone's opinion, but the perspectives of colorblind or blind readers are especially valuable, because using a wrong option might completely ruin the article for them.