Nice discussion. Thanks for putting this together. I learned something about Epistemic rationality vs Instrumental rationality.
The bit about the sky being blue or green seems to beg the question of a justification for objective truth as championed by St Augustine and Leibniz as opposed to arguments for subjective reality as championed by the Cynics and Skeptics and, more recently, the Frankfort school. One could make the case that the sky appears green to one but blue to another.
This topic comes up in many places throughout the history of thought. I'm actually working on a post for my blog exploring that at www.SimplyUrban.Org.