Colo. Rev. Stat. § 22-42-121
Whenever any school district issues bonds under the provisions of this article, the board of education may make and enter in its record a request that the county clerk and recorder of the county wherein the headquarters of such school district is situated register the bonds on a collective, not an individual, basis in a book to be kept by him or her for that purpose. When so registered, the legality thereof shall not be open to contest by such district, or any person whomsoever, for any reason whatsoever. A certified copy of the order of the board, so made and entered of record, shall be furnished to such county clerk and recorder by the board of education and thereupon it shall be his or her duty to register said bonds on a collective basis, noting the name of the district and the amount, the date of issuance and maturity, and the rate of interest of said bonds. The county clerk and recorder is not required to make a separate entry in said book or complete or process a registration form for each such bond of such issue, or otherwise register each such bond of such issue on an individual basis. He or she shall receive a fee pursuant to section 30-1-103(1), C.R.S.
C.R.S. § 22-42-121