In a large bowl, mix together green cabbage, purple cabbage, carrots, and apple. Set aside.
In a medium bowl, whisk together apple cider vinegar. While whisking, pouring in olive oil in a steady stream and continue whisking until it\’s combined well. Season with salt and pepper. Pour dressing over the cabbage and mix well. Top the coleslaw with the celery seed and refrigerate for at least 1 hour.