About twenty years ago, I re-roofed my house with galvalume. The material was available in various colors, but I just bought the unpainted stuff.
The house is at 8500 ft above sea level, which means UV exposure can harm some roofing materials or coatings, such as paint.
So far, there is no degradation to my roof, no discoloration from weather exposure.
About the time I did the roof, I also did several sheds with the generic "barn roof" galvanized sheets. There are a few small rusty places, but they are not structurally problematic. There has also been discoloration. If that matters to you.
I have no experience with the painted galvalume, so I don't know whether it fades.