Lol... no hints on how to remove but this reminds me of a big mistake I made as a working student. One of my jobs was to bathe weekly this large pure white horse. That day he was overall clean just needed his legs, tail, and nose whitened. Well searched around and couldn't find the blue stuff but hey... whats that, purple stuff. Must be a different brand so they colored purple instead of blue, right? (thought that went through my head when I picked it up). Place on dirty areas... wait usual 10 min and rinse.... and rinse... and why the heck is the horse pink? AAAAHHHHHH... it won't come out and the owner will be here soon.
Luckily for me the owner was very understanding... said it matched her lipstick... which it did as she gave the horse a kiss on his pink nose and you couldn't even tell the difference.
I have to say, watching him canter around the arena with his pink tail flowing in the breeze made me want to stick a horn on his head and take pics