That's an excellent question that gets to the heart of design, durability, and maintenance! The answer is: it depends entirely on the bench. The color can come from a surface coating *or* be intrinsic to the material itself, and sometimes it's a combination of both.
Let's break it down. For many classic wooden park benches, the color is indeed painted on or applied as a stain. A solid paint film sits on top of the wood, completely covering its natural grain. A stain, however, penetrates the wood, tinting it while still allowing the grain pattern to show through. Both are surface finishes that protect the wood from moisture and UV rays but will wear, chip, or fade over time, requiring maintenance.
In contrast, the color is part of the material itself for benches made from certain metals, stones, or composites. A bench crafted from naturally rust-colored Corten steel gets its distinctive hue from the alloy's protective oxidized layer. A granite or marble bench's color comes from its mineral composition. Similarly, benches made from recycled plastic lumber have color pigments mixed throughout the entire material, so the color won't scratch off.
Some materials cleverly combine both approaches. Powder-coated aluminum benches, for instance, have the metal's natural silver color as a base, but a durable, baked-on powder coat is applied for a wide range of vibrant, long-lasting colors. The coating is fused to the metal, making it more resilient than traditional paint.
So, how can you tell? Look closely. Does the color show uniform wear on edges and high-traffic areas, revealing a different color underneath? It's likely a surface finish. Is the color consistent even in nicks and scratches? Then it's probably integral to the material. Your choice depends on your desired look, maintenance willingness, and budget. Painted finishes offer limitless color options but need upkeep, while inherent material colors provide longevity with a more natural or industrial aesthetic.