Severus Snape was a thin man with sallow skin, a large, hooked nose and yellow, uneven teeth. He usually dressed in flowing black robes which made him resemble “an overgrown bat”. He had shoulder-length, greasy black hair which framed his face in curtains, curling lips and dark, penetrating eyes that resembled tunnels.

I’m honestly not quite sure about “sallow” (not a native speaker), but his hair certainly isn’t described like the hair of a black person, which AFAIK is universally curly unless they use straighteners, which would be incongruous with how little Snape cares for his appearance. Hooked noses don’t seem typical of black people, either.