Of course, sometimes the bleedin' obvious passes me by.....what colour is
H-Alpha even if you don't have easy access to a solar scope?
Simple!
Just grab a the narrow band H-Alpha filter you are using to image with, and look at a bright white light through it (duh)
Pretty deep red eh?
P.S.
10nm pass filters don't look quite so deep as they obviously pass a little 645nm light...as opposed to 3nm pass versions....they are very crimson.