Plasmablaster, thank you for posting that image of Chernobyl. I really think that the designers should look at real-world examples like that when designing the game.
I understand the nostalgia everyone seems to feel towards that bright colors of the 80s, but I really don't feel like those help to create a dead, decaying, post-apocalyptic world. Playing the original Wasteland, everything's bright yellows and greens and blues. Maybe it's because of the limits on graphics power back then, but those colors really don't give me the idea of a post-apocalyptic world.
Consider the real world, if you will. Humans build things out of concrete, glass, brick, and wood mostly (at least they do where I live). Now, what happens when things are left to their own devices? Plants grow. Mold grows. Things get dirty and grimy. Glass becomes dull and dirty, various vines grow in brick within a few years, and on concrete if you let them. For me, the sign of a place that no one takes care of is plants growing where they really shouldn't be.
That's buildings, but we have other things than buildings, like cars and plastic everything. Plastic decays when left outside, becoming faded and brittle. Cars get dirty, as does everything, and they rust, as do most metal things. Paint peels. Linoleum curls. When you end up with, assuming no plants grow, are pale, dull plastic things, rusted metal things, and probably lots of small debris of the same type.
So, my personal opinion on the color palette that should be used is lots of greens, some brown and red, pale colors in general, and (depending on how long after the apocalypse this game is) a fair number of grays. We shouldn't use pastels because they were used in the 80s. If pastel colors make real-world sense, by all means use them, but please don't use them just to use them.