Hair dye is one of the toughest stains to remove. If it comes in contact with a fibreglass bathtub, there are several options available for removing it. Unfortunately, ordinary soap and water won't work on this tough stain so try these alternatives to remove this most obstinate stain.
Fill the bathtub with hot water and drop in 4 or 5 fizzing denture cleaning tabs. Allow this to sit overnight and wipe clean in the morning with a clean cloth.
Fill the bathtub with water and pour in 3 scoops of Tide washing powder with bleach and two scoops of Oxy Clean. Allow this to soak for an hour and wipe clean with a soft cloth.
Mix borax and water into a paste and scrub the stain with a cloth.
Sprinkle baking soda over the stain and scrub with a clean, damp cloth.
Dampen a Mr. Clean Magic Eraser and scrub the stain out.
Pour bleach on the stained area and allow it soak for at least an hour before scrubbing the area with a clean cloth or sponge.