Sight fishing is not the same as other types of fishing.
When sight fishing with a flyrod, I do indeed use low-light lenses and switch out and back as light intensifies or wanes. On the salt flats, in MJ, that means HT green in low light. In Costas, Sunrise yellow (now mirrored) for low light, and something else later in the day. That’s in the salt. Two will usually do, for me, when sight fishing with a flyrod.
On the open ocean, as in non-sight fishing, I go with one pair of high UV protection, blue mirror or green mirror Costas, all day long. That’s when seeing what’s under water is much less an issue.
Sight fishing fresh water can indeed benefit from more lens colors. There are different water tints, lighting conditions, bottom colors ... copper base is a pretty good all-around, but there are places where a gray base is a huge advantage. Again, here we are talking about optimizing seeing fish to cast to, as opposed to simple UV protection. Those are two very different propositions.
I’ll leave that there ....
Another thing, and I do get crap about this (except from eye doctors), I won’t wear glass fishing, ANY kind of fishing, ever again. It’s shatterproof lenses, always, every time, from here on out, for me.
I took a tiny bead head going a gazillion miles an hour just off the corner of my right eye while flyfishing in Argentina. Totally my fault. Wind was quite strong, gusting, on-shoulder, I was using a two-handed rod, and I was just too lazy to do things like I should have.
Hurt like a mother. Turned into a shiner. And if that little bead head had hit 1 centimeter left on that killer Costa 230G glass lens, the lens would have exploded, with all those shards going into my eye.
I now fish with the most shatterproof, impact-resistant lens I can, ALWAYS. I never fish without shatterproof lenses. I also NEVER shoot without, or run power tools without such protection. I almost, al-most, had to learn the hard way.
To answer the OP: For a free, do everything pair of MJs I would get a general use gray or copper (bronze) base in an impact resistant lens.
