The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
i have pretty good eyes, but i can't really tell if they have a pair hanging down...
Anyway...Generally the males of a particular mayfly species are smaller than the females...
As to color...The variation we think we see could be diet in a particular stream, the color changing after the bug actually frees itself from the nymphal shuck, or we are simply misidentifying the bug we have in our hands.