I see a lot of nymph flies that are tied in different colors. A red Copper John does not look like any nymph I’ve ever seen. Why are there so many nymphs out there brightly colored?
The human eye sees color in only one spectrum, white light. Trout can see color in three spectrums. This is well known science. However, we don’t quite know how color looks to a trout because we can’t see through it’s eyes. This is a very debatable topic is some fly fishing circles. What we know for sure is color of flies do affect trout. Trout can be drawn or attracted to a specific color like red or purple or act aggressively toward those same colors. Good nymph anglers will exhaust there favorite nymphs with little success on a slow day. As a strategy change, they will put on a nymph with a bright color hoping to attract a trout to eat it. You would be surprised how effective this type of strategy can be.