Shred red and green cabbage. (You can use the shredding blade of a food processor; however, I find that cutting the cabbage in thin shreds with a sharp knife gives a better appearance--a method called "chiffonade.") Transfer to a large bowl.
Shred carrots in a food processor or with a hand grater. Add to the bowl with the cabbage.
Place water, tofu, sugar, granulated onion, shallots, vinegar, mustard, salt and black pepper in a food processor and process until smooth.
Sprinkle celery seed over cabbage and carrots. Pour on dressing and toss vegetables to coat.
Allow coleslaw to marinate for at least 20 minutes