Why is my poop green?

The last few days I have been pooping a greenish color. I do not know what it could be from. I have been eating more green salads, maybe 4 in the past 2 days…perhaps it is from that. I am concerned because this is not a normal thing for me. I want to make sure there is nothing wrong here. I tend to hold my bowel movements for a longer period of time so maybe my body is finally telling me something? Any help here would be great! Thanks guys