Short answer: in most cases, yes—but it depends on what the furniture is made of and how it was finished. If you're talking about benches, planters, bollards, or tables in a city setting, I wouldn't just grab a can of house paint. Urban outdoor furniture takes a lot more abuse: sun, rain, salt, foot traffic, and sometimes cleaning chemicals. The repaint needs to be as tough as the original finish.
For powder-coated steel or aluminum, you can often change the color later. A light scuff-sand, a good cleaning, and an exterior-grade metal primer will help, but for a commercial streetscape I’d seriously consider having it re-powder-coated by a shop. That gives you the most durable factory-like finish. If you paint it on-site, use an industrial enamel or direct-to-metal coating and follow the cure time.
Wood is usually the easiest. Sand off loose finish, repair any rot, prime bare spots, and use an exterior paint or stain made for outdoor furniture. Plastic can be trickier—some plastics reject paint—so clean it well, use a bonding primer, and test a small area first. Concrete planters and benches can be painted with masonry paint, but they need to be clean, dry, and fully cured.
A few practical warnings: check the manufacturer’s warranty before you repaint, because some commercial products are voided by site-applied coatings. Don’t paint over rust without treating it, and don’t paint moving parts, threads, or lock mechanisms. If the piece is in a public space, choose a low-VOC, anti-graffiti or slip-resistant coating where needed and let it cure fully before people use it.
So yes, you can usually change the color later. Just match the coating to the material and the level of use. If it’s high-traffic urban furniture, a professional coating job is often worth the extra cost.