That's a great question that gets to the heart of practical urban design. From my experience, the best color for an urban trash can to effectively hide dirt, scuffs, and general wear is a dark, neutral, and matte or lightly textured color.
Think about colors like charcoal gray, matte black, or a deep, earthy green or brown. These darker shades are superior because they don't show light-colored dust, water spots, or minor scratches as easily as light colors do. A bright white or beige bin, for instance, will show every smudge and streak almost immediately, making a city block look messy even if the bins are relatively new.
Furthermore, the finish is just as important as the color. A glossy finish, even in a dark color, will highlight scratches and create visible streaks from rain. A matte or lightly textured finish, on the other hand, helps to break up light reflection and camouflages the small imperfections that are inevitable with heavy public use.
So, while vibrant colors might be tempting for visibility, if your primary goal is to minimize the appearance of dirt and maintain a cleaner look for longer, you can't go wrong with a dark, non-glossy neutral like charcoal gray or forest green. It’s the most low-maintenance and forgiving choice for the tough life of a city trash can.