For a modern plaza, I would not treat color as just a decorative choice. Outdoor furniture has to handle sun, rain, foot traffic, dust, and the way people read a public space. The colors that tend to work best are usually a balanced mix of warm neutrals, deep grounding tones, and a few controlled accents.
A warm neutral base is hard to beat: sand, greige, warm gray, light taupe, or soft stone. These shades feel contemporary without looking cold, and they hide everyday dust and scuff marks better than pure white. They also reflect enough light to keep seating areas comfortable in sunny climates. If the plaza has a lot of concrete or glass, warm neutrals soften the hard surfaces and make the space feel more inviting.
For contrast and structure, use charcoal, basalt, dark bronze, or deep graphite on benches, chair frames, litter bins, or planter edges. These colors visually anchor the furniture and make the plaza feel intentional. They are practical in busy urban settings, although in very hot climates I would avoid large dark surfaces that people touch directly, because they can become uncomfortably warm.
Muted greens such as sage, olive, and deep moss work especially well in modern plazas because they connect furniture to planting and soften the urban edge. For personality, add small doses of rust, ochre, teal, or cobalt blue. These accents are useful for wayfinding, entrances, or social zones, but they should stay secondary. I would also consider accessibility: seat edges and armrests need enough contrast to be seen clearly by people with low vision. Finally, choose durable powder-coated finishes, composite timber, and colorfast concrete stains so the palette still looks good after seasons of public use.