Cook macaroni according to package directions. Drain; rinse with cold water and drain again., In a small bowl, mix mayonnaise, water, vinegar, sugar and seasonings until blended. In a large bowl, combine macaroni, peppers, onion and celery. Add 1 cup dressing; toss gently to coat. Refrigerate, covered, until cold, about 2 hours. Cover and refrigerate remaining dressing to add just before serving., To serve, stir in reserved dressing. Sprinkle with parsley.