Colo. Rev. Stat. § 23-71-515
The bonds issued under the provisions of this part 5 shall be numbered consecutively, beginning with number one. The board of trustees of the district is authorized to prescribe the form of such bonds. Said bonds shall recite that they are issued pursuant to this part 5, and said bonds shall be signed by the president of the board of trustees, bear an impression of the seal of the district, and be attested by signature of the secretary. Coupons, if any, evidencing the interest thereon shall bear the signature of the president of the board of trustees, which may be affixed by him in person, or it may be an engraved or lithographed facsimile thereof. At the discretion of the board of trustees, any bonds may be issued with privileges for registration of such bonds for payment as to principal, interest, or both. In the execution of bonds authorized pursuant to this part 5, the board of trustees may provide for the use of facsimile signatures and facsimile seals in the manner set forth in article 55 of title 11, C.R.S.
C.R.S. § 23-71-515