Wipe hair color dye substance off the surface of the wall with a dry paper towel. Discard the towel in the trash.
Moisten a clean cloth with full-strength white vinegar. Sprinkle baking soda over the cloth.
Dab at the remaining hair dye stain with the vinegar and baking soda cloth. Sponge the stain to work the vinegar and baking soda solution onto the stain. Continue to sponge the stain for one to two minutes to slowly remove the discoloration.
Wipe the wall with a damp cloth to remove baking soda residue and the hair color pigment.
Wet a stain erasing sponge with warm water. Squeeze the sponge to remove excess moisture.
Rub the wall surface gently to remove any last traces of hair color stain. Dry the wall with a clean cloth.