Passing green colored stool is not typically a cause for alarm. Most often, the green color can be attributed to iron supplements, antacids, foods with blue or green dye or leafy, green vegetables. In other cases, green stool can also be a sign of digestive upset or an intestinal virus.But as in your case you are experiencing loose, green stools for more than a week, it is recommended that you contact your physician.You are likely to from suffer from irritable-bowel syndrome (IBS).I would recommend you to undergo few tests. A sample of your stool for culture(Salmonella,Giadriasis etc) blood tests, X-ray, colonoscopy procedure. Salmonella and Giardia infection can cause greenish stool (usually diarrhea).You may then be recommended changes in your diet, in addition to the use of certain drugs for improving the health of your digestive system.