That's a great question, and it's one of the biggest advantages of powder coating. In my experience, the colors hold up exceptionally well over time, much better than traditional paint. I've had my set of powder-coated steel bins on an uncovered patio for about four years now, facing full sun, rain, and snow. While they've naturally acquired a few minor scuffs from use, the color itself is still very vibrant with no noticeable fading or chalkiness.
The secret is in the process. The powder is electrostatically charged and baked on, creating a much harder, more uniform, and bonded finish than liquid paint. This fused layer is highly resistant to chipping, scratching, and most importantly, UV degradation. Manufacturers also use high-quality pigments formulated for outdoor use. You might see a very slight loss of the absolute "brand new" gloss on the surface after the first year or so, but the actual hue remains stable. For maintenance, an occasional rinse with a hose and mild soap is all it takes to keep them looking fresh. So, if you're worried about a bright red or deep black bin turning pink or gray in a couple of years, you can rest easy—quality powder coating is built to last.