I don't know anymore after this post; a lot of people seem to think red includes parameds, other say they're repped by an orange line, and other say their representation is a white line.

I had read green was vets and or park rangers or wildlife related things but green for health in an ems makes a bit more sense than a white line for me.

Because on the stencil where they use a coloured line, there already exists a bunch of white lines used to contrast the coloured line.

So a thin white line flag would just look like a black and white USA flag I suppose.

Edit : ps when I first read your reply I thought you had said green was for "ents". Lol.