From a genetic perspective, human skin color is very, very complicated, but is usually partially dominant, so if people with two different skin colors have children, the children will have a skin color somewhere in between the skin colors of their parents. (black mom + white dad = three mulatto children.)
But what if the genes were different, so that a black mother and a white father might have, say, two white kids, and one black kid?
Or what if the genes were codominant, so that a black mother and a white father's children would have patterns of black and white skin?
What would the effect on society be from this sort of change?