You are not the first Flamingo to get fake pink wrong, Fran, and you won’t be the last! The most important thing to do is stop using the fake pink immediately, otherwise you’ll start glowing in the day as well as the night!
If you then give your body a week to sweat out all the remaining fake pink, you’ll return your feathers to normal; there’s not going to be any long-term problem, so you can lay your worries to rest.
But then you need to think about the future. If you really want brighter feathers, diet is key; make sure you’re getting enough algae, and that it’s the right algae as well, that’s what gives your feathers their colour.
But some of us are destined not to have the look we might want, but that doesn’t have to be a bad thing. Why not own being less pink and strut around calling yourself the fair-feathered flamingo? Then what you saw as a negative becomes a positive; you may even find bright feathered flamingos trying to become paler to look like you!