Come caddis time (which is from about the end of April to the end of the season here) green is a great colour. This is one fly I use a lot, based on the Green Peter, I've called it the Greener Peter
Greener_0001.jpg
There is also another modern twist on a traditional wet fly, the Black Pennel. Its called the Dirty Wreaker and comes in two colour versions, red and green. The photo is of the red version but you get the idea (Sorry couldn't find the photo of the green). Its a Black Pennel with a dyed red or green partridge hackle on the front.
Dirty Wreaker.jpg
One other that gets some use if the Highland Rough Fly in green.
Rough Flies_0010_edited-1.jpg
There is one fly I make sure I am never without on the river. A green aphid imitation. Just a tiny ball of green dubbing which I usually put a turn or two of light blue dun hackle in front of, and sometimes wings of pearl tinsel. Though how important the hackle and wings are I don't know. I have seen trout take aphids in the middle of a hatch of mayflies (danica). What it is about these tiny flies I don't know, but they love 'em.

Cheers,
A.