Combine all the beans and veg in a large bowl. In a small saucepan, combine the vinegar, sugar, oil, celery seed and salt and pepper to taste. Set it over medium heat and bring the mixture to a simmer. Cook for a few minutes, until the sugar dissolves completely. Set the vinaigrette aside to cool for a few minutes before pouring it over the salad. Toss gently to coat all the beans with dressing.
Cover and refrigerate overnight to allow the beans to marinate.