According to an article in Bassmaster, Byron Velvick, among others, recommended the moss green lens for bright sunny days and the amber lens for cloudy days.

I only have a cheap pair of B.A.S.S. polarized shades. They're pretty old but they are better than nothing. If you can afford the Solar Bats, git 'em. I'm just gonna buy a couple pairs of these Bill Dance polarized glasses we have in the store.