Hello. Thank you for coming to JustAnswer with your question, and welcome.
Green stools just mean that intestinal contents (digested food) is travelling too fast through the colon so that the bile contained in the contents does not have time to change to the "normal" brown color.
Another cause could be the foods you are eating, or any vitamin supplements you are taking. There are a few other causes, such as bacterial overgrowth, side effects of medications or recent antibiotic use.
If you are having problems with too fast transit time in the colon, try increasing your dietary fiber intake. Many of us don't get enough fiber. Whole grains, fresh fruits and vegetables, and/or a fiber supplement (such as Benefiber, Metamucil) once a day can help out your colon.
Green stools are generally not a health problem (unless you end up with diarrhea). So, you don't have to worry about this. It will probably clear on its own in some time. But some extra fiber is always good for your colon.
It sounds like you may have a bacterial overgrowth problem. This is most commonly caused by taking an antibiotic, but it can also be caused by a recent gastrointestinal infection caused by a virus or even contaminated food.
You need to eat some yogurt, at least one serving preferably two daily. Make sure you buy a brand that says "live and active cultures" on the label. The "good" bacteria in the yogurt will help get your bowels back to normal. If you can't stand yogurt---you can get some acidophilus or similar capsules at a health food store to take per the labeling directions. (Keep these in the refrigerator to keep the live bacteria healthy).
You also should take a fiber supplement at least for awhile. Metamucil (or its generic psyllium husk powder) is the best for providing the most amount of fiber in the smallest amount of product. Use the powder, not the capsules or wafers. Mix one tablespoon with about 8 to 10 oz of water (it comes orange flavored) and drink once a day. If you really don't like taking this---mix it with about 6 oz of fruit juice but make sure to follow it with a 8 oz glass of water.
Doing both of these daily should get you back to normal fairly soon---within a week or two. You will need to continue this for a couple of months to let your bowels regrow their normal bacteria.
If this does not help, you will need to see your doctor for an exam and some tests to see what else may be going on.