Place the potatoes in a large mixing bowl. Add the diced celery, onion and 3 of the hard boiled eggs, chopped. Stir to combine.
Combine the mayonnaise and mustard in a small mixing bowl.
Add the mayonnaise mixture to the potato mixture and stir to combine.
Transfer the potato salad to a storage container. Top with 1 egg, quartered, grape tomatoes, halved, and chopped fresh parsley. Sprinkle with smoked paprika.