1. In a large serving bowl, toss to combine coleslaw mix, celery, green onion, apple, crumbled blue cheese, and pecans or slivered almonds.
2. In a small bowl, whisk together mayonnaise, Greek yogurt, apple cider vinegar, sweetener, celery seed, salt, and pepper.
3. Pour the dressing over the slaw mixture and toss to coat. Refrigerate for at least 30 minutes, up to 12 hours before serving for flavors to blend. The longer this chills, the better the texture and flavor.