Yes, you can usually paint over outdoor benches if you want to change the color later, but how well the new paint holds up depends on the bench material and the prep work. I have repainted wooden, metal, and even a couple of plastic benches, and the biggest mistake I see is treating them like indoor furniture. Outdoor pieces take much more weather abuse, so primer, paint choice, and curing time matter.
For wood benches, you are in luck. Solid wood takes paint very well once it is clean, dry, and lightly sanded. Wash off dirt, pollen, mildew, and any greasy sunscreen residue first. Sand the old finish just enough to dull the shine—120 to 150 grit works for most pieces. If you are making a dramatic color change or painting bare wood, use a quality exterior primer. Then apply exterior latex or oil-based paint, or a solid exterior stain if you still want some wood texture to show. Teak and other oily woods need an extra step: wipe the surface with mineral spirits or acetone before priming so the natural oils do not push the paint off.
Metal benches can also be repainted easily, but rust is the real enemy. Sand or wire-brush any rust spots down to clean metal, degrease the frame, and use a rust-inhibiting metal primer before the topcoat. Spray paint made for outdoor metal gives the smoothest finish and reaches scrollwork and joints much better than a brush. A clear outdoor topcoat is optional but helps prevent chipping on arms, backrests, and edges where the bench gets the most contact.
Plastic and resin benches are the trickiest. They can be painted, but standard paint often peels because the surface is smooth, flexible, and sometimes has residual mold-release agents. Scrub the bench thoroughly with warm soapy water and a scrub pad, rinse well, and let it dry. Then use a plastic adhesion promoter or a primer specifically designed for plastic. After that, apply paint made for plastic or a high-quality spray paint in several light coats. Even with good prep, plastic bench paint may need touch-ups sooner than wood or metal because the material expands and contracts with temperature changes.
Composite or poly lumber benches are a special case. Many manufacturers say not to paint them because the surface is designed to be low-maintenance and painting can cause peeling or void the warranty. If you really want to change the color, check the brand first. Older composite benches can sometimes be painted after cleaning and using a bonding primer, but I would only do that if the warranty no longer matters.
A quick rule of thumb: if water beads on the surface, paint will struggle to bond until you scuff or prime it. If the old paint is still sound, you usually do not need to strip everything—just clean, scuff-sand, prime any bare spots, and repaint.
No matter the material, wait for a dry stretch of weather. Ideal painting conditions are between 50°F and 85°F with low humidity, and keep the bench out of direct sun while the paint is wet so it does not dry too fast and leave brush marks or rough patches. Light coats always beat one thick coat. Let each coat dry completely before adding the next, and allow the final finish to cure for the time listed on the paint can—usually a few days to a week—before putting cushions back on or leaving it out in rain.
So yes, those outdoor benches can absolutely be painted over to change the color later. Choose the right primer and exterior paint for the material, do the prep carefully, and the new color should last for several seasons.