Really? When I was in the LFS getting my second clown I was looking at a Black Occelaris to pair with my orange occelaris, and I was told that the color difference alone was enough to spark problems between the two.
I believe it, mainly because the guy could have made an $80 sale instead of a $34 sale by selling me a black instead of an orange, but he was strongly advising against doing so.
Now, I don't claim to be an expert, but I trust this employee more than others at the LFS.