Why is his poop so green

He is breastfed mostly and supplemented with formula 0 to 1 times a day very seldom do I give him two bottles of formula his poop is almost always this color consistency changes of course but color very seldom is this a sign of something more he is almost 9 weeks old he has reflux and colic I'm not too sure if he has cow's milk protein allergy but these diapers are starting to make me wonder when I breastfed my daughter hers were always yellow and mustard seedy but my son only had those at the beginning