Bring a large pot of salted water to a boil. Add the eggs, boil for 10 minutes, then transfer to an ice bath. Cook the macaroni in the same water until al dente, about 8 minutes. Drain, rinse with cold water, and let drain well.

Peel the eggs and dice into ¼-inch pieces. Finely dice the celery, bell pepper, and sweet onion.

Whisk together the mayonnaise, mustard, vinegar, sugar, relish, celery seed, salt, and pepper until smooth.

Fold the macaroni, eggs, and vegetables into the dressing until evenly coated. Cover and refrigerate at least 2 hours, preferably overnight.

Stir the salad well, adjust salt if needed, and serve cold with a sprinkle of paprika if you like.