While I really don't like being suddenly confronted with AU elements without a warning (I nearly dropped Applied Cultural Anthropology by jacobk over the changes to Lockhart, and it's one of my all-time favorites), I think Hermione is one of the best characters to race-bend. Like, she's clearly intended to be white in the books, but you could technically apply all descriptions of her to a light skinned brown person and there's nothing about her background that specifically makes her white.

What kind of puzzles me is people who race-bend Harry without outright calling it an AU. Which one of his parents is supposed to be a person of color in this scenario? Because if it's his mother, I don't think it's enough to change Lily and Petunia's hair color. And James is from an old European family. Like, I'm not saying I wouldn't read an AU where Petunia is black, it's just that canon Vernon seems like the kind of man who complains about immigration when he isn't busy hating magic and motorcyclists.

Bonus points if Harry and Hermione are both black, in which case you end up inadvertently implying unkind things about black people's hair.