Colo. Rev. Stat. § 37-41-154
Any person interested in said district, or in the issue or sale of said bonds, or in the making of a contract with the United States may move to dismiss or answer said petition. The provisions of the Colorado rules of civil procedure respecting the motion to dismiss and answer to a complaint shall be applicable to a motion to dismiss and answer to said petition. The person so moving to dismiss and answering said petition shall be the defendant to the special proceeding, and the board of directors shall be the plaintiff. Every material statement of the petition not specifically controverted by the answer, for the purpose of said special proceeding, shall be taken as true, and each person failing to answer the petition shall be deemed to admit as true all the material statements of the petition. The rules of pleading and practice relating to appeals as provided by law and the Colorado appellate rules, which are not inconsistent with the provisions of this article, are applicable to the special proceedings provided for in this section.
C.R.S. § 37-41-154