Is it possible to avoid the radiation that caused the American flag turned into white on the Moon? While lunar images have proven that the American flags planted during the Apollo missions are still standing on the moon, lunar scientists have now said that they probably no longer hold the iconic stars and stripes — radiation from the sun most likely bleached out all the colors. The result? The flags are probably completely white by now. (Source)
The flags were made by Annin Flagmakers. They are nylon and cost NASA very little.  Why so cheap? Didn't NASA know that it would eventually fade away?
What other material could NASA have used to avoid this radiation effect?
 A: White is diffuse reflection - easy and radiation-resistant.  Red could be red iron oxide (works on Mars, yes?).  Blue is a poser.  Ultramarine and Maya blue (indigo intercalcated within palygorskite) probably won't survive vacuum UV.  Cobalt aluminate might survive.  However, smalt loses its color if potassium leaches or is baked out.
It would be interesting to intercalcate pigments within smectite zirconium phosphonates (including pillared after intercalation).  Organics so enclosed have amazing thermal stability.  UV may be different.
Diffraction colors (electro-oxide coatings on aluminum or titanium) would need testing.   Kilowatt elecrodeless mercury low pressure lamps go down to 180 nm emission, with a big spike at 254 nm.  Testing is not difficult.  Ditto commercial multiple-megarad 
Co-60 sterilization or e-beaming it.  
Sounds like fun.  Very pale pink laser ruby becomes magnificent padparadscha pink-orange sapphire give a magarad of Co-60.
A: I would make a flag from iron oxide (red), platinum (white), and lazurite (blue). It won't wave in the wind, but it will retain the color. The base would be a platinum plate, of course. I would made a really large one, so that people wouldn't complain that it was too cheap.



A: The Apollo 11 flag was included almost as an afterthought. It was just a month or so before liftoff, and someone at NASA slapped themselves on the head and said, "we need an American flag to plant at the landing site!" Someone rushed out to a local store (Sears?) and bought a standard nylon flag, which went to the Moon. Besides being bleached out by solar radiation, it was apparently knocked down when the ascent stage lifted off. It's possible that the unexposed side still has some dye left. Later flights carried a flag printed on aluminum foil. The side(s) exposed to the sun are probably bleached by now, if it was a dye/ink/paint and not metal anodization.
Added: I'm not sure where I read about it, so at the moment I can't verify it (possibly an article similar to http://www.collectspace.com/ubb/Forum14/HTML/000753.html). Here are some more descriptions of the process: http://www.space.com/12846-apollo-moon-landing-sites-flags-footprints.html and http://www.hq.nasa.gov/alsj/ApolloFlags-Condition.html (a somewhat official history). 
I had been told somewhere that later flags were aluminum, which seemed consistent with their crinkly look in photos (but, who knows what nylon cloth does at lunar temperatures?). However, the articles all state that all the Apollo flags were off-the-shelf nylon on a special hanger (the Apollo 12 one failed to extend).
