I'm in the market for a second pair of sunglasses, specifically for overcast or dawn/dusk. My primary pair are Costa 580p in green, they are amazing. But when the light drops, it's pretty hard to see. 

 

I tried a pair of amber KK's since they were only $20. Stunning amount of difference in how deep I (can't) see with them. 

 

What color do you recommend for low light/overcast?

 

-These will only be used on the water; I don't care if they are ugly or useless for driving, I do care about being able to see underwater and notice fish. 

-Slight preference for plastic over glass.

-Happy to pay up for good ones.

 

Costa or I've been reading a bunch about Smith (chromapop/ignitor)?

I have the a pair of Smith's Captain Choice Chromapop Ingnitors and so far so good.  They do well early in the morning and especially well at the end of the day.  They are a transition type lens that makes things sort of pink but like a lot of the other high end sunglasses I find that they could be darker during midday.  They are great on glair and sort of make everything clearer and pop.  I do like these exclusively for fishing.  I find that when I fish a lot of coves that go from regular sunlight to overcast/shade that these lenses are fantastic for that situation.  Also, they do a great job of keeping my eyes protected when the boat is moving at high speeds. 

I have a pair of Costa 380G green polorized lense and use them for both driving and fishing. Pricey, but worth it IMO

Look at the Costa Sunrise Silver Mirror lens.

 

They were made for dusk/dawn and low light conditions.