C.R.S. § 14-15-118.5

(1) When parties who have entered into a civil union pursuant to this article subsequently marry, the effect is a merger of the two relationship statuses. Once merged, the civil union terminates as of the date of the solemnization of the marriage or determination of a common law marriage and no separate dissolution of the civil union is required. (2) If one or both parties to a marriage that has been merged with a civil union subsequently desire to dissolve the marriage, legally separate, or have the marriage declared invalid, one or both of the parties must file a petition in accordance with the procedures specified in article 10 of this title. (3) If a civil union and marriage were merged, any calculation of the duration of the marriage includes the time period during which the parties were in a civil union.