Well, I don't want to complain, but I think the same than Noj_R, are Scan effects, if you see a black hair in the light, it gets a shine effect, looking like gray or something similar, that happens to with brown hair, it's only the robot's scan, even the light effects gets in that type scans, you can try it to, take a camera, get a photo of black-haired people in the day, and see the shine in their hair