For the legendary Arizona sunsets, it's nothing astonishing, the orange-and-red blaze hasn't happened yet, but it's still a sort of soft, lovely grade from blue to warm canary yellow--without--and this is the important bit--without ever once turning green.
How you can go from blue to yellow while resolutely avoiding green in any form is something of a mystery, but there it is.
The funny bit is that I remember the sunsets in the Twin Cities, with the peculiar clarity that only someone who took quite a few drugs and sat on a river bank and stared at the sky with the glazed intensity of artificially induced religious experience can recall, and the color gradient DID go to green, then down to a sullen red-orange. (Yes, I did look while I was sober as well, and yes, the green was still there.) It's the same sky, but a different gradient. We also occasionally got powder blue clouds on a sea green sky in a rippled pointy, egg-carton sort of style that looked so bizarre and unnatural it led me to forumulate Ursula's Law of Meterology, namely "If you paint some clouds the way they really look, people think you have no idea how to paint clouds." And if I tried to paint the sky outside as it is now, I would yell at myself for cheap use of a gradient filter. Life is funny that way.
I realize it's probably all just variations on pollutants in the air, but hey, the sky is still cool.