Shred cabbage, green pepper, carrots and onion; sprinkle with salt and let stand one hour.
Boil sugar, dry mustard, vinegar and water for 3 minutes; let cool completely.
After the vegetable mixture sits, drain any excess liquid.
Pour cooled dressing over the vegetables and let marinate for 5 minutes.
Stir thoroughly or cover and shake.
Pack 5 clean pint jars with the coleslaw.
Seal, label and freeze until ready to serve.