Mythology Monday: The Good-looking, the Ugly and the White

My teacher said this was an African myth, but I have no idea from what part of Africa it is and I couldn't find it anywhere else. My teacher kept calling the deity in this myth "Great God" and since I don't know where this myth is from, I don't know if he meant Mumba or someone else, so I'll just call him "Great God". This myth explains why some people are good-looking, some people are ugly and some people are white.

Great God creates all the people, and most of the time he really tries to make the best he can. He gives them handsome features, some nice muscles and keeps everything nicely in proportion. But even Great God gets struck by a case of the Mondays sometimes... On those days  he makes the ugly people, with way to large ears, crooked teath and gangly arms. And sometimes, when he gets drunk, he really messes up and makes white people.