Inter Racial Cuckolding
This is currently a big sub-culture with (mainly) white wives having sex with (mainly) well endowed black males. Commonly abbreviated to BBC (Big Black Cock)
The culture has extended to women having a Ace of Spades tattoo on their ankle as a sign that they love black cock.
There is a smaller sub-culture of black and Asian women using white males to cuckold their husbands.
My husband loves watching me with black guys - he says the contrast in skin colours is great, as well as watching my pussy getting stretched by a huge black cock. (Yep, that is me in the photo!)