It sounds pretty normal to me. Sometimes formula fed babies have green poop because of the iron in the formula.
http://www.justmommies.com/articles/baby-poop.shtml If he's happy there probably isn't a problem. As far as the runniness, Maryella's is usually the consistency of peanut butter, but sometimes when I change her I notice it's runny too. I'm definitely not a doctor, so if you're concerned I would call your ped and see what they have to say.