And if there is, there's an easy answer to questions like "why is a white woman considered more attractive is she has tan skin and a black woman looks better if she has light skin"?
I mean if there is a skin tone that's the most desirable and it's somewhere between the natural skin tone of a white and black person, then it only makes sense that dark skinned white people or light skinned black people would be seen as more attractive; it's not because of a double standard, they'd just be closer to the 'optimum'.
This is also why I think all this talk about people who want to change their skin tone being (by default) ashamed of their race is BS.