Nicely said. I'd like to add that perfect knowledge can only be of the knowable. The non-knowable is irreducibly wondrous and mysterious. The ultimate mystery, why there is something rather than nothing, seems unknowable.
Nice parable, but the author has stacked the deck. The Blues and Greens were originally divided over the issue of the color of the sky. These groups then developed their own cultures and attitudes that had nothing to do with what they believed was the color of the sky, though they were thus identified. The world had evolved to a point that the Blues and Greens had developed mutual tolerance based on a deeper understanding of their common humanity. I suspect that in this new "secular" world, most people viewed the origins of their group name as fictive or ultimately unimportant and the news of the discovery of the True Color would not materially change their lives. The remaining Fundamentalists would, of course, respond in a variety of ways as outlined in the post and comments. It could get ugly but would probably not effect things too much. As the author notes, the discovery of a vast new world waiting to be exploited, would make the people see gold more than it would blue or green.
Not sure why you brought this up, but as long as you did, I'd like to share my resolution of this paradox. Basically, it hinges on the definition of a surprise. If the prisoner is spared on Wednesday, he will know that he is doomed on Thursday or Friday, but is ignorant of which of these possibilities is true. So when Thursday dawns, whatever outcome obtains will be surprising. To say we are surprised by an event is simply to say that we cannot predict it in advance. Therefore, you can only reason about surprise looking forward in time, not backward. Or look at it this way. What if the judge told the prisoner that he was going to draw a slip of paper from a hat contain five slips, labeled Monday thru Friday and execute him on that day. Whatever day is chosen will be a surprise to both judge and prisoner.