In the absence of hard, empirical, unbiased, repeatable data, I will go with the most-appealing-to-me=superstition every time!
I KNOW what the trout sees of the line is mostly a distortion in the mirror surrounding Snell's circle. I KNOW the line appears to be darker to them looking up at it than to me looking down at it. I KNOW the trout see the line color differently than I do due to the difference in our color perception - they see a lot more UV and I see a little more IR. I KNOW a sloppy cast will scare any fish and most animals in the water.
I prefer lighter, earth-tone fly lines because the most-appealing-to-me-superstition is that the best you can hope for is to be seen and not noticed by your quarry.
---------- Post added at 05:05 PM ---------- Previous post was at 05:03 PM ----------
Originally Posted by mudbug
The FLIES have it.