Having lived in a bunch of different areas in the US, I have encountered just as many viewpoints about the race issue:
In Hertford, NC, I was told that the halls were segregated into the '60s, not because the witnesses wanted it that way, but because of the law, and for safety reasons. When the congs integrated, some locals supposedly burned a cross on the lawn of the hall- don't know if this was true, or just an embellishment. In that hall, while I saw no overt hostility, there was also no mixing: there was a white get-together, and a black get-together, held on the same day, and it was just something nobody talked about. For the record, I hung with the blacks, because my two best friends were black girls I went to school with, and as soon as this became apparent, I stopped getting invited to join the white social group. Their loss, I say. My crowd was way more fun.
In Austin, Bastrop, and Smithville Texas, we had a lot of different races/nationalities, and no one seemed to care. I dated a terrific Mexican brother for a while, and my brother married a Central American sister. I got twitted about the 20-year age gap, but the race thing was a non-issue.
In Maine, there are very few people of color. A white sister I knew (she's no longer a witness) was corresponding with a black brother, and there were a lot of raised eyebrows and comments to the effect that apparently, it was the best she could do. I don't know how it ended, but I hope they married and are happy.
In my last cong, a very beautiful and gracious lady from Africa (sorry, not sure which country) was engaged to marry my white cousin, who had just been appointed elder, right about the time I left. I did not socialize much with witnesses at that point, so I'm not sure how people felt about the couple. I do know that my cousin and his bride would not have cared what anyone thought, they were so in love they glowed.
I guess witnesses are like any group of humans as far as that stuff goes- products of their culture, upbringing, and personal experiences.