Hi
My DS had a lot of explosive green poo at around 6-8 weeks of age, it was quite watery and mucosy too. The Paed suggested expressing off the foremilk before feeds for a few days and that cleared it right up. In our case, i'd been on antibiotics a week before and that had given him diahorreah. This can strip the lactase from the gut, making them temporarily 'lactose intolerent', which can cause this sort of green poo 'squirts' (as opposed to regular green poo). Basically, expressing the foremilk gives the gut a chance to recover as it's not having to process so much of the high-sugar stuff.
Have fun with the poos everyone