I had gone through the case and found that if stool consistency is loose and pain in abdomen then must go for treatment it might be gastric infection.
Then go for proper investigation.
But if stool consistency is normal and no abdominal pain
then green stool
might be due to taking of any excessice green v?vegetable. Please notice your diet and medicine if you are taking for quiting of smoking
Hope my answer will be effective for you.