Colo. R. Civ. P. 319
As amended through Rule Change 2024(16), effective September 12, 2024
Persons having a joint interest shall be made parties and be joined on the same side as plaintiffs or defendants. When a person who should join as a plaintiff refuses to do so, or the person's consent cannot be obtained, that person may be made a defendant, or in proper cases, an involuntary plaintiff.
C.R.C.P. 319