Honestly, there is no magic color that never fades in direct sunlight. Fading depends more on the pigment quality, resin, coating, and UV stabilizers than on color alone. That said, if you are choosing a practical color for urban trash cans, light neutral shades are usually the safest bet. Light gray, beige, off-white, and silver reflect more sunlight, stay cooler on the surface, and tend to hide the chalky, washed-out look that fading can create. They are not completely immune, but they often age more gracefully than deep blacks or intense reds, blues, and greens.
White can be an excellent reflector, but in a city it shows dirt, scuff marks, and graffiti quickly. For most streets and parks, light gray or warm beige is the sweet spot: it looks clean, blends with concrete and landscaping, and does not heat up as much as dark colors. If you want a darker color, do not rely on color alone. Specify UV-stable pigments and a good powder coating, or choose UV-stabilized HDPE if the bin is plastic. Black and dark green cans can absorb a lot of heat, which may speed up chalking and color change, especially with cheap paint.
So my practical answer is this: go with light gray, beige, white, or silver for the best sunlight-fade resistance, and put more trust in the coating and UV package than in the color name. A well-made light gray powder-coated bin will usually outlast a cheap vivid-color bin in direct sun. If your city insists on bold colors, ask for UV-stable pigments, a clear topcoat, and a fade warranty, and plan on occasional cleaning and touch-ups.