"stools"=fecal matter, poo, poop, crap whatever.
Never smoked pot so I have no clue about why they might be green. I do know that grape soda, grape juice, and other dietary elements can change the color of your stools. My son went through a grape juce phase...and boy! Wow.
Foods high in iron or iron supplements can turn stool green. Apples, apple juice or pears can cause stools to be green. If you are truly concerned consult your doctor. A culture can be done to rule out any organism causing a problem.
Track what you are using by recording in a Little Black Book-Daily Food Diary and you will discover how your body responds to foods and medications.
I have gallbladder troubles now so I have to monitor and they are bright yellow (gall bladder blocked), golden, bright green (ate cole slaw which is bad for gall stones) and today dark green...but I ate a bunch of blueberries and I am now taking Cipro...so, I can only share my experience...I am not sure if I should be worried or not...I imagine my bile flow is all messed up and food is affecting it, so maybe bile is just over secreting after a gall stone is out of the way... Gall stones occur in young people 20ish and over 40 (mostly women). The pain on my right side comes and goes and is just dull right now.
All the suggestions above are also true. Good luck!