You can use acrylic paint to color and fix discoloration on fiberglass objects. Acrylic paint is latex-based and fast-drying. Dilute it with water to determine the exact red you want to tint an object and if desired, give the effect of watercolor. Depending on the type of acrylic you buy, the finish can have a satin to dull finish. You can also mix in white paint to adjust the color. The best paints are one hundred percent acrylic. When the paint dries, it is water-resistant. You can also mix in gels or pastes to alter the color and saturation. Brands of acrylic paint include Liquitex, Winsor and Newton and Golden. Red can be a problematic color on some objects so you may need to prime the surface with a dark grey primer before tinting to achieve the exact tint you want.
Use a gelcoat to color boats, wind blades, cars and other large structures. Apply gel coat with a spray gun. Thin it with a patch booster, a low viscosity polyester resin, to achieve the tint you desire. You may also need to apply more than one coat to obtain the tint you want. Finish your gelcoat with a sealant and a swirl remover. Gelcoats are available in numerous hues of red from major paint manufacturers. Some companies provide specific colors of red for specific models of boats and cars. As with acrylic paint, use a dark grey primer to prevent problems in not achieving the exact red you desire.
If you prefer not to do the tinting yourself, hire a professional to tint your object with a professional gelcoating machine. Call paint shops and boat maintenance companies in your area to find out if they have gelcoat color tinting machines. Professional tools have dispensing systems that automate the mixing and thinning process. Pros can also show you samples of colors so you know exactly what the finished tint job will look like.
You must prepare the surface of what you are going to tint red. This includes removing any irregularities like scratches and rough areas. You accomplish this by sanding the surface to make it smooth and repairing scratches. Familiarize yourself with proper fiberglass sanding techniques otherwise you could end up with small pinholes on your surface. Do not forget to prime the surface. Major paint companies sell primers specifically for fiberglass.