The color of your poop, believe it or not, matters. An optimal stool is a nice medium to dark brown color, like what you might see in milk chocolate. If it is black, it could be a sign of blood in your upper GI tract. If it is yellow or green, it could be a result of fat malabsorption or liver or gall bladder stress.
Certain foods can also change the color of your stool, such as dark greens and beets, and this is typically not a concern