What does it mean if my baby has green poop?

Stool color: Infant stools can vary quite a bit in color, from brown, yellow, green, orange. All are okay if the baby is otherwise fine and feeding well. Stool should be loose, soft or "seedy". Green stool is not necessarily a reason to be concerned.

May or may not be OK: It may be ok, if the baby is otherwise acting and growing well. But, if it is a sudden change from previous stool color/pattern, green stool may indicate a problem like gastroenteritis - especially if it also has become loose or watery.

OK if baby is OK: You did not mention the age but as long the baby is acting okay it is alright to have a green stool. Most of the time (as long as the stools are not red or black) they are okay.