I assume you don't mean either of the two on the left:



which are pretty common all over the place.

I'm not sure I've ever seen the one on the right--a dual-purpose green that can light up either way. The thing is, if it's not that--if the green can only light up as an arrow--then I don't see why it wouldn't also be a red arrow, and why it would ever be on at the same time.