A fiberglass bathtub is usually repainted because it is old or worn out. Some do repaint it because of its outdated color. No matter what the reason is, you can repaint it in two ways- by hiring a professional or by using fiberglass tub refinishing kits. If you are going to do it yourself, you should prepare the surface first. Clean the surface and fix existing cracks and holes. Remove the fixtures and paint the fiberglass bathtub.