My DD's poop has been that color pretty much always (we pump and nurse, but even when I was EPing - green poop). My son had that color feces because of hindmilk imbalance, but that doesn't appear to apply to DD, and in any case, she isn't having the gas and misery that DS had with that problem, so...
Per extensive conversations with the pediatrician's office about the contents of my daughter's diapers, green poop is within the range of normal. They mention that it can also be caused by mild viral illnesses, and if your babe has just started daycare or something, that's definitely a possibility. But if the baby seems well, healthy, happy, growing, etc., there's a chance that you shouldn't be worried. For my money, I think it's worth giving the pediatrician a call, but not worth losing sleep over.
