when my youngest was getting too much foremilk, she had green poop like you describe...
but she was two or two an a half months old by then...
BUT, if you are nursing a toddler, i assume you're producing a lot more milk than your two week old can handle, which means a lot more foremilk (great for a toddler, probably not so much for a two week old).
you might try pumping for your infant - drain the whole breast and then divide the milk into smaller bottles for him... that way there's a good mix of fore/hindmilk... see if that doesn't clear it up???
this is just theory based on what makes sense according to my own experience... i'm certainly not an "expert!"
either way, i'd definitely check with a lactation consultant or your babies doctor or both (sometimes the doctors aren't all that familiar with the woes of breastfeeding though!).