I've got one colored tat. I don't like the way it looks on my skin.
But hey...that just personal preference. My tat is yellow,green,red and orange. A tattooist once told me purple looks good on dark skin as well.

I'm working on a new tat at the moment and it will be colored.
Why? It's a African mask and it's in earthtones.(clay red,brown,black etc.)
As a rule I try and seek out tattooist who have either a) worked on dark skin. b) are similar in skintone to myself. or c) both a & b.
I usually get better results when I look for these things.