Also switch to LED bulbs as the main lighting in your room. I'd been using regular halogen bulbs and I'm pretty sure they faded some outfits on figures over the years, the Hot Toys T-1000 for example. Upon buying new shirts and pants on ebay I noticed they were a deeper navy than the ones I had had on display for a while.
Some Fading on Barney Ross from EX2. I have the Detolfs and the light is the one that is meant for that display. I don't leave it ON for more than 5 minutes. I don't know if that's the cause or maybe it's just the material.