Shred cabbage and carrots.

Combine green cabbage, purple cabbage, and carrots in a large bowl. Toss to combine.

In a medium bowl, whisk together the mayonnaise, apple cider vinegar, sugar, salt, freshly ground black pepper, and celery seeds (if using).

Pour the coleslaw dressing over the cabbage mixture and toss until combined.

Cover and chill for 30 minutes to an hour before serving for best flavor. Keep chilled until ready to serve.