is it possible to temporarily dye a horses tail with wash out dye?

[First Namesarah K]

So he is an appaloosa with very strange coloring black legs with a gray and brown body with white dapples all over (kind of like a roan). His mane is partially black yet his tail is black at the top yet mostly light grey and very short. I want to get him a tail extension for showing becuase everyone makes fun of his "rat tail". However its hard to find a cheap used grey tail extension. Ive found tons of black ones however....So I was thinking I could buy a black tail extension and then use temporary black hair color to die his grey tail black so it blends in? do you think this would work?

I dont think it would look stange considering he has black legs like a bay and a black mane