Let's be clear that the sun (UV radiation) is a very REAL problem with preserving these fine machines and their vintage paint jobs. While I can sympathize with the fact that the darkness is most annoying, I also can understand that these museum pieces are literally priceless. There has been infinite debates on whether these aircraft should even be flown, so you can imagine how the debate line progresses down the conservation line of demarcation.
Enjoy them for what they are. Soon they will be behind hermetically sealed glass for future generations.