Lightfastness of sign colors

[Pink Jazz]

I would like to know how each color of sign compares in terms of lightfastness.

It seems that green is a color that performs very well in the sun.  Blue seems to be somewhat inferior, since I have seen some blue signs that look faded; this is especially notable on logo signs that had logo panels removed.  Yellow seems to be inferior to green as well, although not severely bad.  The two worst offenders seem to be red and brown.  FYG also seems to perform poorly as well.

I actually wonder if the possibility that green has better fade resistance than blue could be a factor for why guide signs are green?  It does seem a bit counterintuitive that green would be more fade resistant than blue, however, here in Arizona where we get a lot of sun, I have noticed that blue signs generally look more faded than green ones.