Colorado Revised Statutes Title 13. Courts and Court Procedure § 13-40-108. Service of notice to vacate or demand

A written notice to vacate or demand as required by section 13-40-104, 38-12-202, 38-12-204, or 38-12-1303 may be served by delivering a copy of the notice to a known tenant occupying the premises, or by leaving such copy with some person, a member of the tenant's family above the age of fifteen years, residing on or in charge of the premises, or, in case no one is on the premises after attempts at personal service at least once on two separate days, by posting the copy in some conspicuous place on the premises.