This was taken after a thundershower. I'm not sure I like it, because this was the best I could do with the colors without it looking fake. I increased saturation +10, but didn't do much else. Any suggestions?

I don't have any suggestions but I think it's great you had an opportunity to even shoot a rainbow in such classic angle.

Would using a polarizer help next itme for echoback?

Echoback, can you show us the highly saturated version for comparison?

manacsa-that was the saturated version. :) after I edited it, I stupidly forgot to save it as a copy, so I dont have the original, but this is basically the same picture, taken a second before. Nothing was done to this photo for your comparison.

saturation +10 isnt highly saturated ;)

Echoback,

I like the 'original' a little better. The (not highly) saturated version has some unnatural demarkation between the colors. The gradual fade across the spectrum is better in the second shot. (IMO)