pancreatic cancer would have clay/grey colored stools that float.
lettuce can sometimes have a laxative effect on your body. my husband and i joke about "ruffage" all the time as it normally cleans both of us out when we eat too much of it. don't worry.
everytime i do my "green smoothie" i get loose stools that are often tinged green as well. (avacado, kale, spinach, banana) - the next day after eating a more balanced meal-- meat, side, veggie, my stools normally return to being brown.
give it a few days.