1. In a small pan, combine sugar and vinegar. Bring to a boil over medium-high heat, stirring until sugar has dissolved. Transfer to a bowl and let cool completely.
2. Combine coleslaw mix, celery, bell pepper, onion and celery seed in a large bowl and toss with vinegar mixture. Cover and refrigerate for about 6 hours.
3. Drain off excess liquid, season with salt and pepper and serve.