I think you may get a mixed reply, partially because each fish is different but I haven't had any luck mising the black perc's with any others, not true perc's, clarkii's, tomato's etc... they seem much more docile than than the others and get attacked by them.
But go figure, I currently have a pair of black's in my 75g, they were brutal to the 3rd blk clown so he's in a little tank with a damsel and they get along fabulously - who would have thought...