Mecheon
Sacabambaspis
We have void orcs. They're the Pale from Warlords of DraenorI don't know if WoW has any orc communities that got charged up with energy from one of the other cosmic forces (life, death, light, void, order), but it wouldn't surprise me if that would change them into another color.
But they also come in a few other colours. While the mag'har are normally brown, there's a few grey examples of them due to hanging out in mountains, most notably the Blackrock clan (who also get firey red eyes in some cases) and maybe the Shattered Hand, though they're a far lighter grey than the Blackrock