https://www.ginkandgasoline.com/trout-fishing/what-does-the-trout-see
Dec 31, 2013 · The trout’s eye is also more sensitive to the red spectrum than the human’s. The color it has the least ability to discern is green and the color it sees best is blue. Rod cells are very sensitive in low light and give the trout excellent night vision. These cells do not see color. To the rod cell the world is black and white.
i have found that blacks and browns work best in my waters. ive watched the videos of different colored lures under different color waters. black seemed more visible in all colored waters. it is also much more visible to my eye. this makes strike detection easier.
Neil, I also use a lot of black ln my fly patterns. But I include Fluorescent Hot Spot that really POP in the Water Color being fished. Keep the Hot Spots to less than 30% of the pattern’s surface area for best results. With Fluorescent Colors, Less is much better than More…Karl.
oh ya. i add hot spots too…. when i remember 
usually i remember after the fly is tied.
Hi Neil, there are a two ways to solve the memory problem: Use the Hot Spot colored thread to tie the fly with, or go back and wrap on the Hot Spot thread color after the fly is tied…Karl.