To make the bean salad, combine the kidney beans, green beans, white beans or butter beans, optional black beans, bell pepper, onion, celery, and parsley in a large bowl.
Stir together the vinegar, oil, sugar, salt, and pepper. Pour the dressing over the ingredients in the bowl and stir to coat everything well.
Cover with a lid or plastic wrap and refrigerate for at least 8 hours before serving. This will keep nicely for 3-4 days.