1. Bring 3 1/2 qt. water to a boil in a large stockpot. Cook shredded cabbage in boiling water 4 minutes or just until it turns a dull gray purple. Remove from heat; drain well.
2. Cook bacon in a skillet over medium-low heat 8 minutes or just until crisp; remove bacon, and drain on paper towels, reserving drippings in skillet.
3. Stir cider vinegar, celery seeds, and red pepper into hot drippings, stirring to loosen particles from bottom of skillet. Stir in cabbage, salt, black pepper, and bacon; cook, stirring occasionally, 4 minutes or until cabbage is tender and red cabbage turns a bright magenta color. Place mixture in a serving dish, and, if desired, sprinkle with pepper vinegar to taste.