In a large mixing bowl, combine the shredded green cabbage, shredded carrots, and shredded purple cabbage.

In a separate bowl, whisk together the apple cider vinegar, granulated sugar, celery seed, salt, black pepper, and vegetable oil until well combined.

Pour the dressing over the cabbage mixture and toss until the vegetables are evenly coated. Let it sit for at least 30 minutes before serving to allow the flavors to meld.