Nice fish!
I’d have to agree that looks alot like a compara mayfly. The green tail I am going to bet is either caddis green sparkle flash fibers, or could be green fibers with crystal flash alongside of it.
I use allot of crystal flash when I tie up allot of my flies. Especially the newer UV flash incorporated into them.
Have not done the gills yet this yr, but the trout fishing just over the border in WI has been just short of bloody amazing!!
Probably the best yr of trout fishng I have had my whole life!