C.R.S. § 13-1-125

(1) Service of process upon any person subject to the jurisdiction of the courts of Colorado may be made by personally serving the summons upon the defendant or respondent outside this state, in the manner prescribed by the Colorado rules of civil procedure, with the same force and effect as if the summons had been personally served within this state. (2) No service of any summons or other process upon any corporation shall be made outside the state in the manner provided in subsection (1) of this section when such corporation maintains an agent for process upon whom service may be made as provided in rule 4 of the Colorado rules of civil procedure. (3) Nothing in this section shall limit or affect the right to serve any process as prescribed by the Colorado rules of civil procedure.