An old timer once told me this:
To catch a fish, you need to think like a fish
To think like a fish you need to understand that fish do not think!
The moral of the story is that fish act/react. They are animals, living in the animal kingdom.
Their entire life is all about feeding, getting the maximum energy input for the least energy expended and avoiding predators.
Fly lines are not predators, so I suspect then that after 35+ years of experimenting with trout, steelies and Atlantics, fly line colour is not the issue, presentation and food like appearance are the key.
Juro's long sand eel pattern proved that last summer with the bass on the Rip Trip I was so fortunate to be part of.
I know very litlle about salt borne fishies but I did experiment one sumner about 5 years ago with trout.
I fished 40 consecutive days, at the same location and "tested" 21 various line colors, one each day for about 6 hours of casting dry lines, various sink tips and full sink lines.
Conclusion, they all did relatively well.
I then experimented with various leaders.
BIG difference, short leaders with streamers (as short as 6 inches) and progressively longer for the dries and back to shorter for wets/spinners, tippet size to match the fly size 5X being the smallest I used.
I then experimented with various patterns of the same fly at various stages, larvae, pupae/emergers, dry and spinner.
BIG Difference, the most accurate imitations did significantly better than the garden variety.
I then switched rivers and repeated the process.
I then went to several still waters (lakes) and repeated the process.
Overriding conclusion after close to 90 days of experimenting =
1- Presentation & accuracy of imitation
2- Presentation & accuracy
3- Presentation
At no time could I distinguish that line colour had any significant effect of the catch rate.
At the last Rip Trip, I used a 9Wt, level line, chocolate brown, full sink, type 3 and had a blast, no fluoro leaders either. Why? I just did not know any better! I firmly beleive that the fly (Juro's Bad A## Eel) did the trick for me and for the line type and colour I had. Others did equally well with different line colors and different flies and differnet leaders.
I might have done better if ?
Last comment:
Have fun experimenting and keep posting your experiences on the Board. Everyone will learn a little more and we all learn a lot more.
Pete