Historically, the lighter your skin the better you were treated. Speaking of black people specifically, the darker skinned slaves were seen as less intelligent and only good for hard labor. They mostly worked in the fields. Lighter skinned slaves (those of mixed race) were seen as more intelligent than their darker skinned counterparts, but still not as intelligent as white people, they were often used in the house as cooks and nannies and butlers and so on. After slavery, that attitude persisted even within the black community. Black people would put a mixture of lye and potato on their hair to straighten it (called conking) or they'd use oil and a hot comb. There were black churches all over the country that would hang a comb on the door and only allow people who could run the comb easily through their hair to join the congregation. There were social organizations that would only allow people to join if their skin was as light or lighter than the color of a paper bag. And if a person could pass as white, they often did it because it made their lives enormously easier.

During the Harlem Renaissance, there was a push back against these things, but it wasn't until the late 1960s that these ideas about worthiness and attractiveness being tied to light skin really started to die. And they're not all the way dead, there are still black people (and plenty of white people) in America who think kinky hair and dark skin are ugly and that people who have those traits are less intelligent than people who don't.