C.R.S. § 42-6-118

If the owner of a motor or off-highway vehicle for which a Colorado certificate of title has been issued or filed replaces any part of the motor or off-highway vehicle on which appears the identification number or symbol described in the certificate of title and the identification number or symbol no longer appears on the motor or off-highway vehicle, or incorporates the part containing the identification number or symbol into another motor or off-highway vehicle, the owner shall immediately apply to the director or an authorized agent for an assigned identification number and an amended filing of a certificate of title to the vehicle.