Colo. Const. art. XI, § 2

Neither the state, nor any county, city, town, township, or school district shall make any donation or grant to, or in aid of, or become a subscriber to, or shareholder in any corporation or company or a joint owner with any person, company, or corporation, public or private, in or out of the state, except as to such ownership as may accrue to the state by escheat, or by forfeiture, by operation or provision of law; and except as to such ownership as may accrue to the state, or to any county, city, town, township, or school district, or to either or any of them, jointly with any person, company, or corporation, by forfeiture or sale of real estate for nonpayment of taxes, or by donation or devise for public use, or by purchase by or on behalf of any or either of them, jointly with any or either of them, under execution in cases of fines, penalties, or forfeiture of recognizance, breach of condition of official bond, or of bond to secure public moneys, or the performance of any contract in which they or any of them may be jointly or severally interested. Nothing in this section shall be construed to prohibit any city or town from becoming a subscriber or shareholder in any corporation or company, public or private, or a joint owner with any person, company, or corporation, public or private, in order to effect the development of energy resources after discovery, or production, transportation, or transmission of energy in whole or in part for the benefit of the inhabitants of such city or town.