It's normal, my baby poop is like that when I try the Nan optipro, maybe bec too much iron in it but this is normal, I change milk Bec he is constipated with Nan but it's a good brand, he's taking frisolac and his poop ok but still has this green streak as he starts solids
Baby poop colour can be changed with formula. Below article may help you. https://sg.theasianparent.com/baby-poop-guide