I would say you need to go see a Gastroenteorologist if your problems have continued from more then a week. If they have subsided i would still keep a eye on it. Colored stool isn't always a sign of problems, it really is based on your diet and what you eat. But if there is pain and consistentsy with itr then you should definitley consult a doctor.
Change in stool color can happen from taking vitamins, have u recently began taking a multi vitamin? The other symptoms except for undigested food could be from taking vitamins also. Are u chewing ur food well before swallowing? If so and if not taking vitamins my unprofessional advise is to begin drinking plenty of water and get in to ur primary care physician ASAP.
btw i have not changed my diet at all