The former literally segregates users by requiring them to send in a picture with their skin color visible. The latter expresses a racial prejudice in the name.

For example, Reddit previously banned the "fat people hate" subreddit, where they sat around and made fun of fat people, while these subreddits, where all they do is sit around and make fun of people based on the color of their skin are allowed to prosper.

If anything, a subreddit dedicated to making fun of people based on the color of their skin is a lot more bannable than making fun of people based on their weight ..