We used Suave for years because there were so many smells and a good proce, but on my horse that had white areas I used dog shampoo. The dog whitening shampoos are decently priced, and I could wash my Great Dane in it too. :) It worked really well for my horse.
I also use hair bluing for old people with grey/white hair [to make it look white instead of yellow] on my horses white tail, it works really well, but don't leave it it too long ! You can probably get it at walmart