I think that anything that is part of the game is part of the game. That goes for cover image, presentation of the game itself, the blurb, etc. If it releases as part of the game, it’s relevant. Color is no different.
This is consistent with my Infocom criticism.
My color choices are not terribly imaginative or figurative. For Repeat the Ending, I chose an orange-on-dark scheme because orange is thematically significant throughout the game. I chose light purple-dark purple for Marbles and D because a) it reminded me of a grue and b) Marbles has a bit of a regal bearing. I can’t say why the colors in Portrait with Wolf are what they are, but I spent a lot of time with it and the results are what felt best.
I suppose in this way the vague associative nature of PWW makes its colors more thematically significant than those in my other games.
I do check contrast for legibility, as that only seems considerate.