Green winged mayflies?

I went to a local fly shop curious what to use to tie a size 16 mayfly
with orange body and green wings. The guy said as far as he knew
mayflies didnt have green wings. He also said the wings dont matter,
that only the body matters af far as the fish are concerned.

Obviously the fish cant see the top of a dry fly wing, but wouldnt they
be concerned with the under part? The flyshop guy said that the wing is
only for looks and floatation.

Wouldnt also the size of the wing be important? Wouldnt the fish be
concerned with this?
1) what should I use to tie the wing? (size 16 mayfly with green (blends
with green grass)
2) what about what the fly shop guy that said wings arent green?
3) any ideas which mayfly this was just by the color and size given?
4) what patterns would be similiar?