Colo. Rev. Stat. § 40-4-111
The commission has power to establish a system of accounts to be kept by all public utilities, or to classify said public utilities and to establish a system of accounts for each class, and to prescribe the manner in which such accounts shall be kept. It may also in its discretion prescribe the forms of accounts, records, and memoranda to be kept by such public utilities, including the accounts, records, and memoranda of the movement of traffic as well as the receipts and expenditures of moneys and any other forms, records, and memoranda that in the judgment of the commission may be necessary to carry out the provisions of articles 1 to 7 of this title. The system of accounts established by the commission and the forms of accounts, records, and memoranda prescribed by it shall not be inconsistent in the case of corporations subject to the provisions of the federal "Interstate Commerce Act", Part I, 49 U.S.C., sec. 1 et seq., with the systems and forms from time to time established for such corporations by the surface transportation board; but nothing contained in this section shall affect the power of the commission to prescribe forms of accounts, records, and memoranda covering information in addition to that required by the surface transportation board. The commission, after hearing upon its own motion or upon complaint, may prescribe by order the accounts in which particular outlays and receipts shall be entered, charged, or credited. Where the commission has prescribed the forms of accounts, records, or memoranda to be kept by any public utility for any of its business, it shall thereafter be unlawful for such public utility to keep any accounts, records, or memoranda for such business other than those so prescribed, or those prescribed by or under the authority of any other state or of the United States, excepting such accounts, records, or memoranda as are explanatory of and supplemental to the accounts, records, or memoranda prescribed by the commission.
C.R.S. § 40-4-111