Colorado Revised Statutes Title 40. Utilities § 40-5-106. Designation for service of process

(1) It is the duty of every public utility operating in, through, or into the state of Colorado to file with the commission a designation in writing, under oath, of the name and post office address of a person upon whom service of notices or orders in proceedings pending before the commission may be made. Such designation may from time to time be changed by like writing similarly filed. In default of such designation, service of any notice or order may be made by posting such order or notice in the office of the director of the commission and by mailing a copy of such notice or order to such public utility by certified mail, return receipt requested, at its last-known address.

(2) Every public utility operating in, through, or into the state of Colorado shall also file with the director of the commission a designation in writing, under oath, of the name and post office address of a person in the state of Colorado upon whom process issued by or under the authority of any court or board having jurisdiction of the subject matter may be served in any judicial or other proceeding brought against such public utility in this state. Such designation may from time to time be changed by like writing similarly filed. In default of such designation, service may be made upon any agent, representative, or employee of such public utility found within the state. Nothing in this article shall apply to railroad corporations.