The only way to know is through observation Is someone says they have a "True Non-Fading Black", there is no genetic test for it. They just must know that their black horse NEVER BLEACHES OR FADES That's all. Some blacks fade/bleach terribly. And the RARE ONES simply don't. It happens with other colors, too. I have a liver chestnut that fades/bleaches terribly. She is black chestnut with a "fresh/new coat"..but then bleaches out to a terrible reddish-tan color.