Why do stools be in dark color? my stools are ocassionally dark but not black. no foul smell. why?

Bilirubin: in bile, the breakdown product of the hemoglobin in red blood cells, is generally responsible for stool color. Bilirubin concentration can vary the color of stool from light yellow to almost black. Iron supplements can also cause stool to be darker/black. Blood in the stool from upper GI bleeding is usually black; if you have any questions don't hesitate to talk with your doctor about them:)