I agree with the above comments that you should call CO and ask to be reaccomdated. My experience is that they'll work with you to find suitable flights. Since your itinerary involves travel from EWR to SLC (a Delta hub), I'd not only check on CO's flight schedule but also Delta's. If Delta has award seats available for your dates of travel, CO will have the option of reaccomodating you on a Delta flight instead.

I recently called CO to be reaccomodated after a schedule change on an award itinerary and found them to be very helpful. They were able to put me on the specific flights that I requested.