Ok, Ok, everyone step aside. Resident poop doctor coming through.
Jslep is on the money. Generally the cause of green poop is blue or purple-colored food dye, esp in drinks. Like if you drink blue or purple Gatorade or Powerade, you get green poop. Guaranteed, every time. I know, I know, they never taught you that brown+blue=green in your elementary school art class but it does. Not sure how, it's like for some reason the inherent qualities of poop change everything we know about the color spectrum, but it's true.
So no, you don't need to see a doctor. Just revel in the glory of your Kodachrome deuce.
"Somewhere, someone isn't impressed by your looks. Not all men jump through the hoops of your fire. You're unbelievably boring to more people than you'll ever know." --Henry Rollins
"If someone tells you something is easy and they can't explain how to do it, it's not easy." --Steve Shaw