SOme vegetables are green in color, but I'm not sure if I would qualify masturbating with food of any type a "green" activity. It seems like it's more of a food wasting thing, which I don't think is green at all.
The thing about veggies is that they have sugar as a part of their chemical composition, and when used internally, the sugars cause all sorts of uncomfortable infections. So it would be best NOT to masturbate with any food. The nice thing about Eden, and many other sex sites, is that they offer plenty of healthy, body safe insertables
The problem really isn't sugar, as vegetables and fruits are covered in wax, as other things found on the food: bacteria, parasitic cysts (if the food is organic), and pesticides, as well as plain old dirt.
I am not shy I will be honest when I was younger before discovering all these safe and great toys I would use a cucumber. Personally i never had any issues but now that I know better I would not recomend it nor would I do it again.