Shred cabbage in a large bowl and toss with salt. Cover and refrigerate 2 hours. In a sauce pan combine sugar, vinegar, mustard and celery seed. Heat, stirring until sugar dissolves. Remove from heat and allow to cool. Add vinegar mixture to cabbage along with peppers and carrots. Toss to combine all ingredients. Cover and refrigerate at least one week.
Serves 12 to 16