Actually, in reality, the name kenyan just refers to locality more than anything. Much like the rosy boas, they vary in how they look from spot to spot. Except for very rare instances, you would never find wild kenyans that look like the ones we have today in captivity because ours have been bred for their color for so many years, they are now much brighter. So, in some parts of that region, they look orange, in some parts, more yellow. You've heard of the flame race which is still a kenyan, but which has a naturally high orange which stays looking better into adulthood, and then you've got the rufescens which is just another natural morph from a different region. The rufescens are solid color, either a brown or black most of the time. These are all eastern african sand boas, which has been given the name Kenyan.
However, because the rufescens look very similar, at least to the snake catchers over there, like stilletos, which are very poisonous. There aren't many rufescens imported to the US. That is why when they are on Kingsnake, they go for around 2k for a pair.
These morphs aren't a naturally occuring variety that I know of, but they aren't hybrids. The best way to think about it would be breeding different localities in rosies. In fact, the kenyan you most often see is nearly always bright orange because it, too, was crossed with the flame race at some point through the generations.
Hope that clears it up.
Regards,
-Carraig Stanwyck