Yentle, if the horse is very black around the eyes and muzzle I would only use clear makeup. But that's only because if it's already black, black makeup won't change it and it can be messy. I'd rather get clear makeup on me than black, so why use the black if it doesn't make a difference. You can get a black makeup that is a stain and it will temporarily dye hairs black, but it does dry to a matt finish so it's not really ideal. The good thing is though that once it dries you can rub your hands all over it and you won't get any black on you. Personally I would just dye the mane and tail to get rid of any sun bleached bits. If you go to the supermarket and buy the Just For Men range in the colour that you need, it's brilliant stuff and the best bit... it only takes 10mins for it to process and then you wash it off.