Yes, you can paint over most outdoor benches later if you decide to change the color scheme. The short answer is yes, but how well it turns out depends on the material, the current finish, and how much prep you are willing to do. I have repainted several outdoor benches over the years, and the difference between a finish that lasts and one that starts peeling in a few months usually comes down to cleaning, sanding, and priming.
If the bench is wood, repainting is very doable. Start by cleaning the surface with mild soap and water or a deck cleaner to remove dirt, mildew, and pollen. Let it dry completely. If the wood has a clear sealer or old paint, sand it lightly to rough up the surface and remove any gloss. If there is loose or flaking paint, scrape it away and sand the edges smooth. Bare spots should be primed with an exterior wood primer before you apply the new color. For topcoats, use an exterior latex or oil-based paint that can handle sun, rain, and temperature swings. A clear exterior topcoat is optional, but it can help high-traffic areas like the seat and armrests hold up longer.
If the bench is metal, you can also repaint it. Wrought iron, aluminum, and steel benches respond well to spray paint made for exterior metal. First remove any rust with a wire brush or sandpaper, then clean the metal with a degreaser or soapy water. Rinse and dry it completely. Apply a metal primer, especially if you have bare metal or repaired rust spots. After the primer dries, use light coats of exterior spray paint or brush-on metal paint. Light coats give you better control and reduce drips. If the bench has a powder-coated finish in good condition, you do not have to strip it; just scuff it lightly with fine sandpaper or a liquid deglosser so the new paint can bond.
If the bench is plastic, resin, or poly lumber, painting is trickier. These materials are smooth and flexible, so standard paint may scratch or peel. Some people have success with a bonding primer designed for plastic, followed by an exterior spray paint. Even then, plastic benches will not be as durable as a factory finish. In many cases, changing the color on plastic furniture is easier with outdoor cushions, slipcovers, or replacing the bench.
A few tips apply no matter what material you are working with. Do not paint over a wet, dirty, or chalky surface. Do not skip primer on bare wood or bare metal. Use paint labeled for exterior use, because interior paint will not handle moisture and UV exposure. Lightly sand between coats if you want a smoother finish, and let the final coat cure for at least a few days before placing heavy items on it. If you are changing from a very dark color to a very light one, a good primer is even more important and you may need an extra topcoat for even coverage.
So if you are wondering whether you can paint those outdoor benches over later, yes, in most cases you can. Match the prep and primer to the material, choose an exterior-grade paint, and your new color scheme can look clean and hold up for years. The key is not the color change itself; it is the preparation underneath.