What color nail polish do you like?
I use all different colors. Right now my toes are lavender with silver sparkles. I have done black on them too, it's really pretty in my opinion. If I am undecided I just go with the regular old red, it's a sure fire color that matches everything.
I don't paint my fingernails though. I cannot stand chipped nailpolish so if I bother to paint them it might last a day. Kind of a waste of time.