If you want to wade into the subject of anodizing, how it's done, what can go wrong, etc. you can visit a forum that deals with industrial metal finishing. A couple to get you started:
Black anodized parts fading - Non-UV cause
Fade Resistance of Color Anodized Aluminum
Most fading is probably from UV exposure but it can occur from temperature, how the parts were processed (sealed or not, prep work done prior to anodizing, etc.) and a host of other things. Note that different dyes have different fade resistance, even within the same color family. Worldwide, there are probably hundreds, if not thousands, of dyes available.
JR