Why is there a preference for light skinned women? Is this preference universal?

Gabrielle Union, is GORGEOUS. I know dark females that are very pretty and men like talking to them. My husband may find me attractive but before me he dated dark skinned women because he said light skinned women are to stuck up and self absorbed and that the darker the realer you are. One can also say "Tan" women are preferred universally also, I know white guys that won't date a white woman that don't tan.