My girl is black and I have tried them all. the ones that say they are just for blacks to enhance the shine and I have to say never thought that much of any of them, and now I use Johnsons Baby Shampoo, its gives the best finish and you do not have to use that much of it to get a good amount of bubbles. When you see the price of these shampoos that are just for horses and the price of this one there is no comparison. Hope this helps
I know your horse isn't classed as a coloured, but I use Groomaway's 'Just for coloureds' shampoo and it makes the dark patches really shiny AND makes the white patches really white so I would definitely recommend it.