Your gall bladder is green, bile is green. Infection can be green. Mucous can be green. This is why snot is green. Snot is mucous surrounding stuff we breathe in and getting it out of our bodies. When you wake up with eye crispies that are green, it is our bodies' way of excreting things from our eyes that would be bad for us. These are all the green things I can think of in our bodies. I am not a doctor, though. Just a wannabe.