or if your Google-fu is strong, you'll know that Chrysaor is traditionally depicted as a black winged boar, not a winged horse. But you know, like most of the characters in Sailor Moon, his relation to Chrysaor is through name only.
I read a long time ago that the original concept for the SuperS movie was going to involve Uranus and Moon getting into a race, with Usagi riding on Pegasus, and Uranus riding on a black Pegasus. Personally I thought that would be a ridiculous plot for the movie (it's a rare occassion where I can say that animated candy would make MORE sense), but the idea of a black Pegasus struck me as interesting, so that's the inspiration for this character.
I sorta see what you did thar
I physically turned upside down in a better effort to recognize those reflections in the pool. One of them I recognized immediately, the other...I doubt I was supposed to (right?). But the black Pegasus' reflection does appear to be that of a one-legged (or standing on one foot, anyway) man. Hmm....