Colo. Rev. Stat. § 38-36-161
Whenever a mortgage upon which a mortgagee's duplicate has been issued is assigned, extended, or otherwise dealt with, the mortgagee's duplicate shall be presented with the instrument assigning, extending, or otherwise dealing with the mortgage, and a memorial of the instrument shall be made upon the mortgagee's duplicate and upon the original certificate of title. When the mortgage is discharged or otherwise extinguished, the mortgagee's duplicate shall be surrendered and stamped "canceled". In case only a part of the charge or of the land is intended to be released, discharged, or surrendered, the entry shall be made by a memorial accordingly in like manner as before provided for a release or discharge. The production of the mortgagee's duplicate certificate shall be conclusive authority to register the instrument therewith presented. A mortgage on registered land may be discharged in whole or in part by the mortgagee in person on the register of titles in the same manner as a mortgage on unregistered land may be discharged by an entry on the margin of the record thereof in the county clerk and recorder's office, and such discharge shall be attested by the registrar of titles.
C.R.S. § 38-36-161