Darker colors, particularly reds, purples, and blues, will still last many years, but may show fading sooner than lighter ones. Many manufacturers will warranty their products against significant fading or chalking. Polymer paints tend to be the least expensive, but are also are usually only warrantied for about 10 years against fading and chalking. Other products are usually warrantied to last longer, some even for 35 or 40 years! (Most other roofing surfaces would need replacement much sooner than that.) The color can last even longer than that, too, with proper maintenance. Even after the color has faded, the metal roof can be repainted with high quality paints to give it new life.