Colo. Rev. Stat. § 13-72-103
In drawing the list of jurors, the court shall select from no less than seventy-five names thereon and from such additional lists of names as the court may order, or from such lesser number as may be called to serve as jurors, the names of either twelve or twenty-three persons who shall constitute a grand jury and four alternate grand jurors. The members of the county grand jury shall be selected by the chief judge with the advice of the district attorney. The court may close to the public part or all of the selection process when reasonably necessary to protect the grand jury process or the security of the grand jurors. The length of term served by a county grand jury shall be as provided in section 13-71-120. The court, upon its own motion or at the request of the district attorney, shall enter an order to preserve the confidentiality of all information that might identify grand jurors when reasonably necessary to protect the grand jury process or the security of the grand jurors. In the absence of such an order, upon request, the jury commissioner shall make available for inspection by members of the public a list of grand jurors containing only the grand jurors' names and juror numbers. The court may strike the name of any juror who appears to the court to be incompetent or unqualified to serve.
C.R.S. § 13-72-103