The things others have said are true--
watch out for the ingredients in the dressing (you want to avoid sugar in the first three ingredients, hydrogenate oils of any kind, and any high fructose corn syrup),
make sure it has less than 3g of sugar, and,
if in Phase 1, avoid carrots in the coleslaw mix.
However, making homemade coleslaw is really easy. I do it all the time! I just use a Betty Crocker recipe and use splenda in place of sugar.
Ours is, I think:
1 cup of mayonnaise (feel free to mess with this...use part yogurt or whatever)
2 packets of Splenda
2 Tbsp of white vinegar
salt, pepper, and celery seeds to taste
I throw all of it in a ball canning jar, shake vigorously, then spoon out with a rubber spatula into a bowl of the coleslaw mix. Instant coleslaw!
I always add some of the "broccoli slaw" or "rainbow slaw" mixes to the bag of coleslaw mix for extra nutrition.
There's a recipe for Overnight Coleslaw in the SBD book (or cookbook?) that one of our Beachies
adored. She even made it for breakfast!
I haven't tried it, but it sounds good.
I've found tons of great coleslaw-ish recipes online. One of my favorites is an apple slaw made with the coleslaw bag, cut up apples, a little bit of sunflower seeds, and a vinaigrette dressing. Yum!