Posted 5/7/2013 7:34 AM (GMT -5)
Black blood comes from the stomach (food-poisoning, stomach ulcers, etc). Dark red comes from somewhere in the small intestine (high or low depending on darkness). Red and bright red comes from the large intestine. The brighter red the blood is, the fresher it is, which indicates how close to the rectum it originates. If you had really bright red stuff it could be from a hemorrhoid near the rectum, or irritation in the rectum from the tip of an enema bottle.
We all have a hint of blood in varying colors from time to time in our stool. It isn't anything to worry about if you see it only the once. If it is something you are seeing with regularity then it indicates something serious you should get checked out.