Could Foul Smelling Green Color Stool Indicate Lactose Intolerance?

Hi my baby is nearly six months old and been on SMa lf milk since he was about a month old as we thought he might be lactose intolerant but it was never diagnosed now the gp has put him back on normal baby milk and told us to see how he reacts and to do a stool sample now his stools have gone from the normal yellow colour to runny very dark green colour very nasty smelling too and he's crying a lot more after feeds and has a lot of gas is it likely to be lactose intolerance.