Boondocks can be considered anime since it's drawn by an anime studio. There are only like 4 white characters in there.
BTW Yoruichi isn't black, she's just dark skinned. The reason why there aren't many black characters in anime is because animes usually take place in Japan and there aren't that many black people in Asia in general. During the 5 years I lived in China, I only remember seeing 3-4 black people in the city and most blacks stay in the airport/beijing tourism area.
Multinational animes tend to have more black people but still... there just aren't that many.
Only black character in Full Metal Panic but the commander of the badass team who still likes watching Miyazaki anime.