The requirements for both parties are the same:
18 and older - No parental consent is required
16 and 17 - Consent of both parents, or the parent having sole legal custody, or guardian, or judicial approval is required
Younger than 16 - Consent of parents or guardian and judicial approval (court order) are required, no exceptions
Valid identification must be furnished by both parties, i.e. passport, birth certificate, driver's license, military ID, etc. If the applicant does not have a Social Security Number, an affidavit must be completed and notarized at time of marriage license application.
As of July 1, 1989, blood tests are not required.
A couple may not marry when one of the parties is still married to another person. Divorces must be final. Date and place of divorce are required on the marriage application form. Marriage between brother and sister, uncle and niece, or aunt and nephew is prohibited. Marriage between cousins is permitted in Colorado.
Couples themselves can solemnize their own marriage (C.R.S. 14-2-209). Others who can solemnize a marriage are judges, retired judges, magistrates, public officials authorized to perform marriages, or in accordance with any mode of solemnization recognized by a religious denomination, American Indian tribe, or nation. Not anyone can solemnize a marriage. Although the couple may solemnize their own marriage, that does not mean a friend or relative can also solemnize their marriage. Clergy from out-of-state need not be registered in Colorado.
Witnesses are not required in the State of Colorado.