Crisp the coleslaw mix. Toss 16 ounces coleslaw mix and 1 cup thinly sliced purple cabbage in a large bowl with ¼ cup sugar and ¼ cup kosher salt. Transfer to a strainer and place it in the sink or on a plate to catch moisture. Let it sit for 5 minutes to draw out moisture from the cabbage, then rinse with very cold water. Spin the coleslaw mix in a salad spinner or pat dry with a tea towel, and place back in the bowl.
Mix it all together. Add 2-3 chopped green onions, 1 julienned carrot, 1 diced celery rib, ¼ cup chopped parsley, and ½ cup Ranch dressing. Season with ½ teaspoon kosher salt and ½ teaspoon ground black pepper, and toss well. Add more dressing and adjust seasoning as desired.