Green diarrhea may simply be showing the normal bile in your stool. Since you have diarrhea, your intestine is rapidly moving the contents out of the body. Bile is normally found in the large intestine, and at a slow rate, much of the bile undergoes a chemical reaction and changes the stool brown. At the accelerated rate, the bile does not have time to undergo any chemical reaction and diarrhea will come out green. For more information, go to http://www.medicinenet.com/stool_color/article.htm.