Here's some of the info you may have been looking for:
green frothy stools are caused by a lactose/fat imbalance (meaning the baby is getting higher volume, higher lactose content milk - i.e. oversupply)
fat content of milk varies throughout the day - when volume is high, so is the lactose content and when fat content is high volume tends to be lower
fat content of milk can vary throughout a feeding, but it isn't determined by beginning or end, but how...