Everyone's eyes are different but for my retinas high quality grey lenses provide the best color fidelity while the ambers are known to enhance contrast.
I can't see taillights when I wear amber so to keep my insurance down I wear grey or copper lenses most of the time.
I found that the grey gives me color differentiation which sometimes is the only thing that clues me in (other than motion) where the copper are better during low light and when contrast are key.
Successful sight fishing is much more than just eyes. Seeing is just the tip of the iceberg so don't leave out the mountain of logic, luck and spidey sense that brings you to stake out a spot with conviction.
IFFF Certified THCI @ 2005
Capeflyfisher Guide Service
Island Hopper, Guitarist, Incurable Dreamer
and Founder, Worldwide Flyfishing Forum