Fiberglass pools are one of the primary pool construction options next to concrete and plaster. Fiberglass pools are created as large shells that are installed in one large project, making installation fast and relatively easy. Because fiberglass is all one running piece of matting and resin, including the steps, leaks do not form in the pool as easily. However, fiberglass will only hold specific types of paint.
The gel coating on fiberglass pool steps is necessary to protect the fiberglass. This coating should always be used, no matter what type of paint you have. If you need to repaint part of your fiberglass pool, you will need to strip off this fiberglass coating and replace it after you have added the paint layer. The gel coating is typically clear but is much thicker than paint and helps prevents wear and leaks in your pool.
If you want to go beneath the gel coating layer and actually paint the fiberglass itself to change the color, you need to use an epoxy paint. These paints are made from chemical compounds that harden into a strong, waterproof layer necessary for fiberglass protection. These epoxy paints may also be able to fix small chips or cracks in your fiberglass.
Some fiberglass pools are painted with multiple layers to create different effects before they are installed. If you have a fiberglass pool with several color and gel coat layers designed to make the perfect texture or shade, you will have a lot of trouble mimicking that same color. A single new paint coat will not be able to match the original work. Consult a professional for advice on how to best imitate the previous color of the pool.
Beyond gel coats and epoxy paints, you should not be using any other substance to paint your fiberglass pool. Other paints will quickly corrode or will not adhere properly in the first place, causing the paint to peel and dissolve and potentially harming the fiberglass beneath it. Only use paints designed for both pools and fiberglass materials.