If you plan to make a fashion statement with your bike, definately worry about the color. If you plan to simply enjoy your bike, get one in a color you like. If you plan to race your bike, get one that will look like a blur zipping by the competition.
I've been to TOO many MTB races, and I think that black MTB bikes look more like they mean business than any other color, but that doesn't hold for road bikes.
__________________
As with mud, life, too, slides by.