Boil the macaroni in salted water according to the package directions until al dente.

Drain the pasta and rinse it under cold running water to stop the cooking.

In a large bowl, whisk together mayonnaise, sour cream, mustard, and vinegar.

Add the diced celery, bell pepper, and red onion into the dressing.

Fold in the cooked macaroni until every piece is coated well.

Season with salt and pepper to taste.

Cover and refrigerate for at least one hour before serving.