Heres a pic of the view of the Discovery shuttle tiles at work in space.

pretty pic, i wonder why some are black and others are white, the white ones i believe are ice, but i wonder why it doesnt cover the rest of the bottom of the shuttle.

That is a neat pic. Although I don't know for sure, but my guess would be that the reason for some of the tiles being black while the others arn't would be just that some tiles are older and more dirty than others. They don't replace every tile after each mission, just the ones that really need it, so the black ones are probably the newest ones. Not 100% sure on that though.

jra may be right about the age difference, I would come to that conclusion too. Just for the fun of it, I think it may be ice, due to impurities in the silicon some took longer than others to cool than others did, so ice formed on the tiles that cooled down first. But I'm still going with what jra said.

i agree with jra, the other ones arn't white there more of a grey, because they have in previous missions allready done firey re-entry, and are kinda chared from it, while the black ones are new and have yet to experience the 3000 degrees F.

On the topic of cool pics, here's one from the fuel tank, showing the underside of the shuttle: