Sorry, I don't know the answer to your question about green beans. However...
My current favorite bean salad:
one can of chickpeas or kidney beans, drained and rinsed
one round of fresh buffalo mozzarella, cubed
a few vine-ripened tomatoes, cubed
fresh basil (a small handful of whole leaves, don't bother chopping them up)
aged balsamic vinegar or white balsamic vinegar
flavorful extra-virgin olive oil (1 part vinegar to 2 or 3 parts oil)
salt and fresh ground pepper to taste
Mix it all up and let sit at room temperature for about 30 minutes to an hour. Summer in a bowl.

I was just helping someone who needed simple summer recipes. My summer salads are seriously tasty. Here's the basic idea (copied and pasted here from my advice to my friend):
The base salad recipe, choose one or more from each category:
1. beans, lentils, quinoa, pasta, rice, barley, bulgur, other grains or meat
(chicken, turkey, tuna, etc.)
2. Vegetables: tomatoes, bell peppers, zucchini, cooked peas etc.
3. Herbs: fresh basil, oregano, thyme, etc.
4. Acid: any variety of vinegar, lime juice, lemon juice
5. Oil: olive oil (2 or 3 parts oil to 1 part vinegar)
6. salt and pepper, to taste
optional additions:
1. cheese
2. toasted nuts or seeds
When it comes to method, there are two choices:
1. put everything together when it's cold or room temperature
2. add just-cooked and still-hot lentils (or whatever) straight to your
salad ingredients--this will wilt spinach or rucola and warm all the
ingredients, making things slightly more flavorful.