I have a supposed white faced dog but it has stained pink- the groomer thinks it is water stain but nothing is getting rid of it. We have tried various shampoos, leave in shampoo. stain remover (for dogs!) and leave in paste.
The colour is similar to tear stains. As we have a show in 2 weeks I/m getting desperate. I thought my daughter was too when she went looking for the Vanish but it was for my t-shirt!
He also has a purple paw since deciding to empty the contents of a 2L bottle of dilute blackcurrant on my floor.

Have you tried a bicarb of soda whitening tooth paste - use an old tooth brush and scrub - obviously rinse thoroughly after.

Have you tried one of the stain removing horse shampoos?  Or Hilton Herbs 'Ocean Blue' shampoo which can be left on for 10 minutes before rinsing?

Eye Envy is an excellent product it's american & they don't have an agent over here but you can order it directly from their website