Colo. Rev. Stat. § 1-40-120
In case a complaint has been filed with the federal district court on the grounds that a petition is insufficient due to failure to comply with any federal law, rule, or regulation, the petition may be withdrawn by the two persons designated pursuant to section 1-40-104 to represent the signers of the petition and, within fifteen days after the court has issued its order in the matter, may be amended and refiled as an original petition. Nothing in this section shall prohibit the timely filing of a protest to any original petition, including one that has been amended and refiled. No person shall be entitled, pursuant to this section, to amend an amended petition.
C.R.S. § 1-40-120
This section is similar to former § 1-40-109 (2)(b) as it existed prior to 1993.