If you go to my timeline (you can stalk me, I'm honored when ppl
   look through my public past), about a month ago I posted a few
   facts about Ultramarine Blue and Indigo. The very color itself
   protects the skin against UV damage - blueberries, grapes, wine,
   cranberries, dye #2... all related. Might be the same chemical
   structure, but probably simply be how that color protect best
   against dangerous colors. "