Colo. Rev. Stat. § 30-6-105
When a majority of the taxpaying electors residing in that portion of the territory of any county proposed to be stricken off and annexed to an adjoining county shall petition the board of county commissioners of the county in which such territory is situate to have such portion stricken off and annexed to the adjoining county, giving the area and general boundaries of such territory by natural objects and monuments as near as may be, and shall deposit with such board of county commissioners an amount of money sufficient to pay the expenses of the surveying and platting of such territory, it is the duty of the said commissioners to have such territory surveyed and platted in a suitable manner and to cause to be submitted to the registered electors of such county at the general election next after the filing of such petition and plat with them the question of whether such portion of the territory of their county shall be so stricken off. The board of county commissioners shall also require the county clerk and recorder, in giving the notice required by law of the general election then next ensuing, to insert therein a notice to said registered electors that the question of striking off such territory from their county, particularly describing such territory by metes and bounds as shown by said survey, will be submitted to them for their approval or rejection and that they should designate on their ballots their approval thereof, which shall be expressed by the words "for the new county line", or their dissent thereto, expressed by the words "against the new county line". The board of county commissioners of the county to which such territory has been annexed may, in their discretion, pay the necessary expenses of such survey and plat by warrant on the treasury as in other cases.
C.R.S. § 30-6-105