I am constantly mystified why anglers I meet have fly boxes stuffed with dozens of patterns and yet they only cover a couple of sizes which are nearly always 14s and 16s . Personally I beleive that fly size and correct presentation is almost more important than the pattern.
I have given up wondering what the exact dressing Cannon Greenwell beleived was correct as every text you read seems to give a slightly different pattern. However I tie a well waxed yellow thread body with a light gold rib and a few hackle fibres as a tail. Hackles vary I will occasional go very light using a golden badger hackle but mainly though the colours I use are below...There is an Indian cape and a genetic neck and saddle cape
The Greenwell is one of the easiest of ties which suits me I like quick simple flies that I am happy cast into tight places and risk losing. Also I dont like using winged patterns. I find winged flies lead to leader twist and offer no appreciable advantage over hackle only patterns.
The fact is both the Greenwells and the Kites Imperial in a range of sizes and hues and tied on varied hook patterns tied sparse and full will I beleive provide more fish in the net than a load of patterns in a ltd range of sizes, They work very will tied parachute style as an emerger pattern as well. I think It was said that Oliver Kite used his imperial pattern to the exclusion of all other dry patterns and he certainly knew a thing or two. Give them both a go you wont regret it.....