Colo. Rev. Stat. § 16-5-203
Whether a prosecution is commenced by indictment, information, or felony complaint, the district attorney shall make available to the defendant not later than twenty-one days after the defendant's first appearance at the time of or following the filing of charges a written list of the names and addresses of the witnesses then known to the district attorney whom he or she intends to call upon at trial. The district attorney shall also furnish the defendant in writing prior to trial the names and addresses of any additional witnesses who have become known to him or her prior to trial and whom he or she intends to call upon at trial, but this shall not preclude the calling of witnesses whose names or the materiality of whose testimony are first learned by the district attorney upon the trial. However, the court may, in its discretion, enter an order that denies the disclosure to the defendant of the names and addresses of witnesses, or that requires the defense counsel not to disclose such information to the defendant, subject to rule 16 part I (d)(2) and part III (d) of the Colorado rules of criminal procedure. The names and addresses of witnesses who are the subject of the order may be withheld pending a ruling of the court, but the prosecution shall notify the defense counsel in writing that a motion to withhold witness information has been filed and that such information will be withheld pending the court's order. Where the defendant has not had or waived a preliminary hearing, there shall be filed with the information the affidavit of some credible person verifying the information upon the personal knowledge of the affiant that the offense was committed.
C.R.S. § 16-5-203