How do you get hair dye out of a ceramic bath tub?

Bleach

If it's truly a ceramic tub try some scouring powder. Don't try this if the tub is fiberglass or acrylic, though. And if that doesn't work, try a little bit of plain old laundry bleach, making sure to wear rubber gloves and ventilate the room well while you are using the bleach. Soak the stain well with the bleach, wait ten or fifteen minutes, and rinse the tub out well. Follow with regular tub cleaner. Just be sure not to mix the bleach with any other household cleaners, as certain chemicals mixed together give off deadly fumes.

I agree w/ the above comment , Mr clean magic eraser has done wonders for my tub .. i dont have to let chemicals sit for a few either , just grab the eraser and get to work , its worth a try for hair dye :)

Try Mr Clean eraser.It worked on mine