According to the Mayo Clinic, clay-colored stool is pale or white rather than the usual brown color. Because stool gets its brown color from bile released by the liver, clay-colored stool is a possible sign of a bile duct blockage or liver infection. Medline Plus notes that other causes of clay-colored stool include hepatitis, tumors in the liver, cysts of the bile ducts, gallstones and the use of antidiarrheal medications containing large amounts of bismuth subsalicylate.
As noted by the Mayo Clinic, stool color is determined by foods that are consumed, as well as the amount of bile present in the stool. Consumption of leafy green vegetables, iron supplements or green food coloring can cause stool to be green. If food passes through the digestive system too rapidly, stool may also be green.
Bad-smelling stools that are yellow and greasy indicate the presence of excess fat, which may be due to a malabsorption disorder. Consumption of gluten can also result in this type of stool.
Black stool may indicate bleeding in the upper digestive tract, but the consumption of black licorice, certain iron supplements and bismuth subsalicylate can also cause stool to appear black. Bright red stool may indicate bleeding in the lower digestive tract or bleeding from hemorrhoids. Eating cranberries, tomato products, beets or foods that contain red food coloring can also cause bright red stool.