Colo. Rev. Stat. § 31-23-106
In case of filing any such plat under this part 1, the designation by which any lot, block, or other parcel of land has previously been known shall be retained in said plat. With the consent of the city or town, any such lot, block, or other parcel of land specified in said plat may be designated by other numbers or names than those by which said lots, blocks, or other parcels of land have been previously known. Such consent of any such city or town, through its governing body, shall be evidenced by the acknowledgment of the mayor. In case of tracts or parcels of land within any such city or town which have not been known or platted by lots, blocks, or other parcels of land of a designated number or name, the same may be platted as provided in section 31-23-105 upon the consent of the city or town as provided in this section.
C.R.S. § 31-23-106
This section is similar to former § 31-1-406 as it existed prior to 1975.