Place red potatoes in a pot and cover with water. Place pot on stove, cover and bring to a boil. Liberally salt water with coarse salt. Place a colander over boiling pot. Take your first ingredient from the bean salad, 1/2 pound cut fresh green beans, and place them in the colander. Cover the colander with pot lid. Steam beans 5 minutes while potatoes boil below. Remove beans and cold shock under running water. Drain green beans and set aside.
When the potatoes are just tender, about 12 minutes, remove from heat, turn off burner, drain potatoes and cold shock them under running water until just cool enough to handle. Coarsely chop potatoes and return them to the warm pot. Add peppers, onions, mint, parsley and vinegar to the pot. Toss to allow the vinegar to absorb into the potatoes. Add oil and stir the potatoes until they mash up a bit and salad has a spoonable consistency. Season with salt and pepper, to taste, and transfer to a serving bowl.
In a bowl, combine mustard, sugar and vinegar. Whisk in oil. Add kidney beans, garbanzo beans, green beans and parsley to the bowl and toss to coat bean salad evenly with dressing. Season salad with salt and pepper, to taste, and serve.