Breastfed, what color is your babies poop?

Meech
Lately my LO seems to have trouble having a poo. He grunts and cries and seems to be in discomfort until lately it explodes from him or foams out and is usually green in color with a constancy of water. I've mentioned it to my doctor and he says that some babies actually try to hold it in. The grunting isn't them pushing it's actually them trying not to push. Just worried that maybe he's not getting any hindmilk. This morning his poop was green and totally absorbed into his diaper...is this normal?