If you want loads of detail on CVD then there's a long thread in the Professional Pilot Training forum:
http://www.pprune.org/forums/showthread.php?t=229604
I've posted quite a bit on this as I've been really looking into it all. Most of the discussion is about Class 1 but as far as I can tell the Class 2 colour is effectively the same as Class 1. IE if you fail the ishihara plates then you will be issued with a class 2 restricted to daytime VFR only (you can't do a night rating). To get this restriction removed you have to pass a lantern test, which is what you would be given during a Class 1 anyway...
Good luck to all. CVD sucks
