noun, の adjective
A black person is simply a black person, kind of like how a 白人 is a "white person," but a different color.
This is a jukugo word, which usually means on'yomi readings from the kanji. Since 人 has two on'yomi readings, here's a mnemonic to help you remember which one to use:
Imagine a black person you know well wearing coke jeans (こくじん). Yep, jeans made entirely from coke bottles. That's actually a thing. Look it up if you don't believe me.
Tokyo has a big community of black people.
There are still not many shampoos and foundations for black people in Japan.
My mother is black and my father is Asian.