Cut the fresh green beans into 1-inch pieces, then steam and let them cool. Dice
the red onion. Whisk
the vinegar, oil and salt and pepper together in a bowl with a tight fitting lid, then add the green beans, garbanzo beans
, red kidney beans, and onion and seal with the lid. Shake gently to coat the beans and then refrigerate overnight. Serve chilled as a salad or side dish.