Wasn't there a black guy in one of Ashley's pics? When she talked about anal no less. Or was it just really tanned dude or bad lighting? Point is that if it already happened and nothing blew up it should be fine to have someone like that appear again without much problem.. Keep on certain paths and with choice to reject and everyone should be ok with it no? I actually have a sneaky suspicion the "big burly men" Ashley talked about who would help move the bed could be black, but I have no proof of that just a feeling.
One of the flaws of AI CG games is that characters often look similar and it's easier to make females look varied than it is to look guys varied. In this sense, skin tone change is very easy way to make characters seem varied, cause if you start having multiple color hair guys they will feel too feminine in most cases and that will not roleplay well with the "bull" theme.