Causes of changes in stool color include diarrhoea, consuming a particular food, diseases of the pancreas, liver and intestines, and certain medications and supplements, says MedicineNet. Normal stool color includes all shades of brown and green, reports Mayo Clinic.
Diarrhea and green leafy vegetables are common causes of green stool. Iron supplements, black licorice and bleeding in the upper digestive tract cause black stools, states Mayo Clinic. Yellow stools that are greasy indicate excess fats in the stool due to diseases such as celiac disorder. Bleeding in the large intestines or rectum leads to bright red bowel movements. Eating beets, red food coloring and cranberries can also cause red bowel movements.
Changes in stool color necessitate consulting a doctor to check for serious complications such as pancreatic disorders and other underlying causes, advises MedicineNet. Changes in stool color that occur as a result of eating certain foods resolve within a few days.