First of all, there shouldn't be any cause for concern just because your bm's are greenish colored given that you eat a lot of green vegetables. I eat a good amount of chlorella and spirulina, and the only way you know if you're eating enough of them is if your stools are green. I guess the chlorophyll does partially make it through the digestive tract.
Can you eat too many? It would probably take some doing given that many people (again like myself) do vegetable juicing where it would be nearly impossible to eat the amount of raw greens in their native states that are being consumed as juice on a daily basis.
If you get some big reaction (other than green colored stools) you can back off them a bit. But I have no doubt the good you're doing yourself by consuming lots of green vegetables puts you at the top of the class health regimen-wise.