One would have to assume that the red tail acted (or acts) as an attractor, an ‘excitor’ to the trout. But, you would be hard pressed to find many fly tiers that use red in their patterns these days. I am not talking about Steelhead patterns, but rather the trout patterns. I think red tails are perhaps worth a try and purple, hot green, blue, orange….  Water clarity and depth can influence the color spectrum and visibility. Experiment with some colors.