Colo. Rev. Stat. § 30-6-106
Upon the receipt of the said petition and deposit by the board of county commissioners, they shall immediately give notice of the fact to the board of county commissioners of the adjoining county to which the petitioners desire said territory should be annexed, and the board of county commissioners of the adjoining county shall, upon receipt of the same, require the county clerk of that county, in giving notice of the next general election, to notify the electors of that county of the proposed annexation, particularly setting forth by metes and bounds in said notice the description of the said territory, that the question of such annexation will be submitted to them at said election, and that said electors shall designate on their ballots their dissent from or agreement thereto, which dissent or agreement shall be expressed as is provided in section 30-6-105.
C.R.S. § 30-6-106