The color of stool can be affected by the things that we eat. Normally stool is brown which comes from pigments released from the bile. If the stool becomes white in color this indicates significant problems with the bile flow and needs to be looked into medically. Yellow or green color usually indicates temporary, short lived conditions. One of the signs for things called polyps or cancer of the colon can be bleeding.
Blood can be red clots or black in color with sticky fowl smelling stools.
Frequently, this is not due to cancer, but in all cases should be evaluated by your physician. The consistency of stool should be soft and should hold together. It should sink and not be extremely offensive smelling. If it falls apart, has mucous in it or has a strong odor it indicates that you need digestive support. Normal frequency of bowel movements should be once or twice a day.