To a large bowl, add purple cabbage, coleslaw mix and cilantro.
In a small bowl, whisk together mayonnaise, sour cream, lime juice, Splenda, celery seed, and mustard powder. Pour dressing over cabbage. Mix until thoroughly combined. Season with salt and pepper, if desired.
Refrigerate at least 30 minutes before serving for flavors to blend. The longer this chills, the better the flavor!