I seem to see those posted on here quite often, not sure if they are undigested food though... Green color probably indicates it was in the gall bladder area for a while before coming out....
I would keep doing the herbals you are using and keep watching the stool to be safe, it's possible it is undigested food, but also possible it is part of a parasite life cycle.
Looks similar to what you see. If it was undigested food, why would so many people have photos of them. Not giving ideas but keep your eye out ;-)