Colo. Rev. Stat. § 24-60-206
On the trial in any of the above-named compacting states of one charged with a crime therein committed, if any person within any compacting state is wanted by either party as a witness in such trial, said compacting states, their courts, and their court officials will recognize as valid any subpoena, summons, or court order issued or made in accordance with the law of the compacting state where trial is to be had for the appearance of the person in said state where trial is to be had as a witness at such trial, the same as though such subpoena, summons, or court order had been duly issued or made by a court of the state where said witness is found; but a resident of a state so called upon to attend as a witness in another compacting state shall not be required to attend unless and until there is paid to him compensation, including mileage, equal to that provided by law of the state requiring attendance, for the time he necessarily would be gone from home; and further, he shall be immune from the service of civil or criminal process upon him while in attendance at said trial and when en route to and from the place where he is to testify, as to all matters occurring prior thereto.
C.R.S. § 24-60-206