I can't speak to subspecies or anything similar, but that color mutation is called "anerythrism" and results from the absence of red pigment. It's quite common in corn snakes and has cropped up in many constrictors as well. This animal, if collected, would probably have been worth quite a lot in the captive-bred exotics market as an outcross strain for existing anerythristic lines in banded Lampropeltis cultivars.
