Colorado has adopted the Uniform Marriage Act at C.R.S. 14-2-101, et seq. So the Colorado statutory procedures parties must follow in order to marry may seem familiar to those who have been married in other states.

Ceremonial marriage is what most people think of when getting married, and contrasts to common law marriages, which are also recognized in Colorado. 

Procedures

1. Marriage License.  The parties must obtain a marriage license from your local county clerk and recorder, providing basic demographic information.  No blood test is required.  If a party is divorced, proof of the divorce must be furnished.  C.R.S. 14-2-105.  Though both parties must sign the license, only one of them need appear in person to obtain the license.  C.R.S. 14-2-106.  The license fee in El Paso County (click here for more information) is $30.
2. Solemnize the Marriage.  The license is void if not used within 30 days, pursuant to C.R.S. 14-2-107, so make sure it's solemnized in time.  Though parties typically have a judge or minister perform the ceremony, Colorado allows the marriage to be solemnized by a judge, magistrate, minister, or even one of the parties to the marriage!  C.R.S. 14-2-109.
3. Register the Marriage.  The person who solemnized the marriage must complete the marriage certificate form, which must be forwarded to the county clerk & recorder within 60 days of the ceremony.

Marriage by Proxy

When one party to a marriage is not available to attend the ceremony, Colorado allows the marriage to be by proxy, which means that a third party stands in for the unavailable party.  C.R.S. 14-2-109(2).  The following criteria must be met:

1. The absent party must be unable to be present,
2. The absent party must consent to the marriage,
3. The authorization ("proxy") must be in writing, and
4. The person solemnizing the marriage must be satisfied that the absent party is unavailable and has consented to the marriage.

Age Restrictions

Colorado requires that each party to the marriage be at least 18 years-old, or at least 16 years-old if that party has the consent of both parents/guardians, or the parent with decision-making responsibility over the party.  C.R.S. 14-2-106.  Children under 16 years-old may marry with both parental consent, and permission from a judge.

Judges can approve a party who is 16 or 17 years-old providing that:

1. The party's parents/guardian approves, and
2. The court finds the marriage serves the best interests of the under-aged party (note that pregnancy alone does not establish that it's in the party's best interests to marry.

Penalty for Improper Marriage

Colorado law provides that it is a misdemeanor to attempt to knowingly violate the procedures and requirements for a marriage.  C.R.S. 14-2-113.