To be quite honest it wasn't their skin colour that caught my eye, mate. 
Actually, I am pretty sure that the cleavage that L'Ursa and B'Etor (I think that that is how their names are spelled) had was actually prosthetic, just like the Kahns big ol' macho pecs in
Wrath of Khan and the rather well documented exotic dancer in
Total Recall. Part of the outfit.
Eye catching no doubt, but fake from the outside in (rather than the more commonly seen fake from the inside out, like the Vulcan in
Enterprise).
And that ends my first and last ever online comment about Star Trek cleavage.