Green beans...when to pick them?

The beans are ready to pick! I've found that my yellow beans matured more quickly than the green and purple (most likely due to the variety, not color).

The question is when do I pick my green beans? The photo above shows new beans needing some growth.

The purple beans above could be picked or I could wait. The photo below shows a better comparison. 

The green and purple are small but edible. I'll call them "baby beans," and they're tender, but then I'm getting the bulk I might need for a meal. The tiny ones don't freeze well. I like to pick beans before the seeds inside start to develop. The one on the far right has the beginnings of seeds. Many people pick the beans when they're thick and fat, with clearly developed seeds inside. That's okay, too. When I lose track of beans and they get that big, I cook them a little differently, chopping them into bite-sized pieces and cooking them longer to tenderize them. When I pick them small, I'll eat them raw or lightly cook them, under a minute in the microwave. No matter when you pick them, they're delicious!