Black was a Human racial classification associated with a "black", brown, or otherwise dark skin color and African ancestry. Individuals described as such were black people. Negro or colored were terms sometimes used to refer to black people.
In 2375, Benjamin Sisko had a problem with a holosuite program which took place in Vic's lounge in 1962 Las Vegas, Nevada. In 1962, black people weren't very welcome there. They could be performers or janitors but never customers as the Civil Rights Movement was still in its infancy. (DS9: "Badda-Bing, Badda-Bang")