Red used to be a hot spot of sorts for fly patterns. The fly patterns that sat in plastic bins in hardware stores (pre-flyshop/online sales days) sometimes had that red hackled-fibered tail. There has been a recent spurt of hot colored beads and hackles that allow for that insertion of a bright ‘hot spot’ to perhaps attract the take.
If you do any research on colors and their visibility in water, you learn the color red supposedly fades first as it descends down through the water…past depths of 10 feet. Is it even worth the effort to include a hot spot? Is red even visible on that tail or beard (suggesting gills or blood)? Well, I have experimented with hot colors of orange, blue, chartreuse, red and have had the best results with red.
Experimentation is a very special part of fly tying and fishing for me and many fly fishers. Experiment with colors. Sometimes it is a one time success and sometimes the experiment yields years of special moments. All part of the fun.