Negro, colored, and n*gger were terms used for people of African ancestry or appearance (such as having dark skin or being black) throughout the English-speaking world until the mid-20th century.
In an alternate timeline 1944, while walking with Alicia Travers, Jonathan Archer was asked by a German if he liked Negroes. He was then told, "When we send her back to Africa, you can go along. You can run through the jungles together." (ENT: "Storm Front")
During Benjamin Sisko's vision of 1950s America, Benny Russell and other people of color were often referred to as Negroes. Herbert Rossoff once joked about the dangers of a Negro with a typewriter. Jimmy suggested that people of color would never get into space except as shoeshiners, because "as far as they're concerned, we'll always be n*ggers." (DS9: "Far Beyond the Stars")
The Excalbian recreation of Abraham Lincoln referred to Nyota Uhura as "a charming Negress" before realizing that his words were poorly chosen. He corrected himself by stating that in his time, "some used that term as a description of property." Uhura, however, asked why she should object to that term, explaining that Human philosophy of the 23rd century taught mankind not to fear words and to be delighted with who they were. (TOS: "The Savage Curtain")