Paul got a pretty high percentage of the black vote in Kentucky in 2010. Something like 32%.
It might be too small a sample size though. Kentucky doesn’t have a large black population like much of the South, I think it’s about 92% white.
If the GOP ever wants to get a significant black vote, it will have to be for candidates who are seen as outsiders or at least average people.
The Bush/ McCain/Romney silver spoon types are intensely distasteful to minority voters.