What Causes Abdominal Pain And Green Colored Stools?

Hello, My question is why would my stool be green for the past 3 days? I have had no cramping, some have been lose some haven't, i don't feel like anything is wrong. I have had a cold, but i have had many forever and don't remember green stool like that. I also started nuvaring a few days ago. I am also on phentramine (generic for Adipose) to helo in weight loss but ive been on that for a while and never remember green stool. I just recently went to my obgyn, and no std's and i didn't get blood work but ive been tested for aids and all the normal stuff and never had anything come up. I also don't remember eating anything with blue or green dies in it. I did a few times feel a dull/to sharp pain between the stomach and gall bladder area after i ate, but i don't have a gall bladder anymore and i havent felt that in a few days either, Why would my stool be green in color for so many days, and again some were soft some were firm, but i don't feel like anything could be wrong, i feel i am my normal