The flavor of green Jello is lime.
Lime Flavor Jello comes in a green color and is really good.
All Jellos also contain pork which makes the gelatin.
The pork bones are boiled which makes a protein called collagen come out of the bones and that collagen protein is what makes the Gelatin that makes Jello.
Marshmallows also use the pork bones as well as other things such as gummy bears etc.
So if you're vegetarian then you will want to avoid Jello, Gummy bears and other things that contain Gelatin.
Some types of Jello might be vegetarian but not all are.