It ain't gonna happen (that Apple will bring these colors back). I miss them, too, and was aghast to find them missing. But Apple clearly is intent on making Mac more like iPad, with the Finder being faded into non-existence. No Finder, no colors.
Just look at the recent announcement of Mountain Lion; the whole message is that from now on, Mac takes its cues, its look and its feel, its operating principles from iPad. End of story. (Which makes a lot of sense, product positioning-wise, for the more Mac looks and feels like iPad (a far more popular machine, at this point), the more Windows-owning iPad owners will feel comfortable switching to a Mac, too, if it's really a desktop machine they want.)
We can complain, we can whine, we can protest, but nothing, I believe, will change Apple's mind about this. Big people - perhaps Mr. Jobs himself - have made big decisions, and if nothing else, they are not about to admit the mistake they have made and reverse themselves.