sofadog wrote:
Help my window sill (installed with upvc windows) is splattered with
hair dye. I've tried everything to remove it. Or should I try to
paint over it, if so with what?

It's certainly possible if you buy special primers & paints etc, but upvc
doesn't really like to be painted and the surface may not be that durable.

Perhaps worth considering replacing the sill, or fitting a new upvc fascia
board on top of it. Something like this :