This has been asked many times before. I quote Thomas Hughes April 23 2007:
"David C, Please register my vote to incorporate a color-correction ability just like FCP's, where you simply find something in the picture that should be white, click on it and it corrects all of the other colors based on that white.
It's really magic. Why can't Media 100 have it?"
It still would be nice not to have to switch to FCP to do this extreme helpful color correction!