Can I give chickens un- dried beans?
Dried beans have to be cooked first, and I think green ones probably should be too.
Beans have a toxin called phytohaemagglutinin, that affects people and also livestock (presumably including chickens.) It's destroyed by boiling for some amount of time. Some beans have a lot more of it than others. (I got all that from the internet, so I can't be positive it's accurate, but it is repeated many places, including wikipedia.)
I also find accounts of chickens eating a few dry beans when allowed in the garden, with no apparent ill effects-- so I would not deliberately feed them large amounts uncooked, but I would not panic if they helped themselves to a bit here and there. Chickens are fairly good at avoiding dangerous plants when they have lots of choices.