I used goof off liquid and comet cleaner formed into a paste. I left it there for a day or two and when I cleaned the paste it was gone.
How Do You Remove Hair Dye From Porcelain Sink?
You can use a normal cleanser like comet. If the stain doesn't seem to be coming off, try a little toothpaste on an old toothbrush. If all else fails, try some bleach.