Abnormal stool colors include white, which means there may be a lack of bile in the stool, or yellow, which indicates there may be too much fat in the stool, according to Mayo Clinic. Light-colored stool may also occur due to the use of anti-diarrheal drugs, and yellow stools may occur due to eating gluten, which is in bread or cereal. Other unusual stool colors include green, black and red.
Green stool can be normal in many cases, especially if the person is eating a lot of leafy greens or foods with green food coloring, explains Mayo Clinic. However, green stool may also indicate that food is moving through the intestine too fast, and the bile does not have time to break it down. Black stool may indicate that there is bleeding in the stomach or other organs of the upper gastrointestinal track. It may also occur due to iron supplements, black licorice or the use of medications with bismuth subsalicylate, such as Pepto-Bismol or Kaopectate.
Red stool may also occur, and it might indicate bleeding in the rectum, large intestine or another organ in the lower intestinal tract, claims Mayo Clinic. Hemorrhoids may also cause red stool as may eating food with red food coloring, cranberries, beets, tomato products or red gelatin.