This is my own experience, which may not reflect recommended practice!
For drying, the beans are left on the plant until the shells have started to turn brown. They can be left to go completely brown. The beans are then harvested, shelled, and can be left to dry indoors. I have picked beans for eating fresh at any time once the beans have formed, which is easy to tell by feel . . . The shells will have turned a stripey red at this point.
I dont have any more to add, good luck!