I like black because it makes your teeth look really white, that's why they use dark skinned people for toothpaste commercials. their teeth look really white against their skin, same with contact lense commercials they use dark skinned people with light eyes blah blah blah.
I think you should take a dark color, because light colors tend to get yellow and then it looks bad, so pick a bright colour! I think purple, green, blue and even pink, depending on how dark it is would look awesome.
Do NOT get light blue!
They may look pretty for the first few days, but if you eat foods with artificial coloring (especially yellow) they will change colour.
I ate some chicken salt when I had my light blue ones (it seemed innocent enough) and the went FLURO GREEN.
My recommendations include dark purple (they look awesome) and pink.