Green poo - sorry!!!

I have been breastfeeding by LO for 11 weeks now and since about 6 weeks, his poo has starting changing from bright yellow to green. Its not everytime but he seems to do yellow poos every day but one may be greeny pale brown. I asked my HV who is rubbish may I add, and she said he has colic but I know that he doesn't. He settles easily, sleeps from 7pm till 6am (I never planned for a baby that would sleep through but I am so glad he does!!!) but I don't know what else it could be. I feel like maybe something isn't agreeing with, even though he never seems to have tummy pains. Has anyone else experienced this? Any suggestions would be greatly appreciated!!! Thanks girls.