what can make your stool dark green
Green: 1  Green stools are always normal, but they can be mistaken for black stools. 2  Bile. Most dark green stools are caused by bile. 3  Green stools are more common in formula fed than breastfed infants. It can be normal with both.  Green stools are more common with diarrhea. This is due to a fast transit time through the gut.