Please refer to text of above cases, but in very brief summary:  Common law marriage is recognized in Colorado.  Graham v. Graham, 130 Colo. 225, 274 P. 2d 605 (Colo. 1954)  

        There can be no common law marriage where the agreement is that the marriage contract shall be by future ceremony.  In re Danika's Estate, 76 Colo. 191, 230 P. 608 (Colo. 1924)

        Cohabitation is presumed to be matrimonial; but that is a presumption of fact, not of law.  When there is evidence against the marriage, the cohabitation becomes an item of evidence to be considered with all other such items, and it is strong or weak according to the circumstances.  An agreement to live together as man and wife is not necessarily marriage, but is open to the interpretation of an illicit relation resembling that of marriage.  In re Foley's Estate, 76 Colo. 286, 230 P. 618 (Colo. 1924)

        Principles set forth in Graham v. Graham, 130 Colo. 225, 274 P. 2d 605 (Colo. 1954)

       The only essential requirement of a valid marriage contract between parties capable of contracting is their consent, but the contract alone is insufficient, unless consummated by the parties' cohabitation as husband and wife.  

        If the marriage is denied and can not be shown, its existence may be proved by and presumed from evidence of the parties' cohabitation and general repute as husband and wife.  Cohabitation required to consummate marriage contact means not merely sexual intercourse, but living together in the same house, claiming to be married, or the act or state of dwelling together or in the same place.

        General reputation or repute of a man and woman as husband and wife, as required to establish a common law marriage, means the understanding among neighbors and acquaintances with whom they associate in their daily life that they are living together as husband and wife and not in meretricious intercourse, and it involves social conduct and recognition giving character to admitted and unconcealed cohabitation.

        There must be evidence of both cohabitation by and reputation of a man and woman as husband and wife before common law marriage can be presumed.

        The determination of weight of evidence and reasonable inferences therefrom are for the trial court in a case tried without a jury.

CRS 14-2-110. Prohibited marriages.
        (1) The following marriages are prohibited:
                (a) A marriage entered into prior to the dissolution of an earlier marriage of one of the parties, except a currently valid marriage between the parties;
                (b) A marriage between an ancestor and a descendant or between a brother and a sister, whether the relationship is by the half or the whole blood;
                (c) A marriage between an uncle and a niece or between an aunt and a nephew, whether the relationship is by the half or the whole blood, except as to marriages permitted by the established customs of aboriginal cultures.
        (2) Children born of a prohibited marriage are legitimate.

CRS 14-2-111. Putative spouse.
        Any person who has cohabited with another to whom he is not legally married in the good faith belief that he was married to that person is a putative spouse until knowledge of the fact that he is not legally married terminates his status and prevents acquisition of further rights. Children born of putative spouses are legitimate. A putative spouse acquires the rights conferred upon a legal spouse, including the right to maintenance following termination of his status, whether or not the marriage is prohibited under section 14-2-110, declared invalid, or otherwise terminated by court action. If there is a legal spouse or other putative spouses, rights acquired by a putative spouse do not supersede the rights of the legal spouse or those acquired by other putative spouses, but the court shall apportion property, maintenance, and support rights among the claimants as appropriate in the circumstances and in the interests of justice.

CRS 14-2-111 provides that any person who has cohabited with another in the good faith belief that he was married to that person is a putative spouse until knowledge of the fact that he is not legally married terminates his status and prevents acquisition of further rights.  A putative spouse acquires the rights conferred upon a legal spouse, including the right to maintenance, whether or not the marriage is prohibited under CRS 14-2-110, declared invalid, or otherwise terminated by court action.  Combs v. Tibbitts, 148 P.3d 430, 433 (Colo.App. 2006).