01 - Bring a large pot of generously salted water to a rolling boil. Add the red, white, and blue potatoes and cook for 12 to 15 minutes until fork-tender. Drain thoroughly in a colander and set aside to cool slightly.
02 - In a large mixing bowl, whisk together the mayonnaise, sour cream, Dijon mustard, apple cider vinegar, salt, and black pepper until the dressing is smooth and creamy.
03 - Add the cooled potatoes, diced celery, sliced green onions, chopped parsley, and fresh dill to the dressing. Gently fold and toss until all ingredients are evenly coated, taking care not to break apart the potato pieces.
04 - Taste the salad and adjust the salt and pepper as needed to suit your preference.
05 - Refrigerate for at least 1 hour before serving to allow the flavors to meld. Serve chilled or at room temperature.