This one's particularly confusing because grannom refers to the genus brachycentrus. Then the question is which species.
I'm no bug expert, but I think two species are important: Americanus (American Grannom) and Numerosus.
I think Americanus is the brown wing, green body. Numerosus is the gray body, dark (almost black wing). I wonder if you're getting the two confused (or heck, maybe I'm just plain wrong)?
I fish the b. numerosus hatch every april. Green body/black wing ESP's and DSP's work as does the classic starling & herl fished down and across. Mercer's Z-wing pupa is a good
'un as well. For the adult, I like a grey body, black wing with the hackle tied up front like a stimulator (not palmered on the body).