Under Colorado law identifying information may be exchanged when the adult adoptee (age 21) and the birth parents have each filed consents. Relatives of deceased birth parents and relatives of deceased adoptees may also register.

Information will only be released if both birth parents register UNLESS (1) only one birth parent is listed on the original birth certificate, (2) only one birth parent is still living, or (2) the non-consenting birth parent is unable to be located after a diligent search.

For registry information, contact: Colorado Voluntary Adoption Registry, Colorado State Department of Health, 4210 E. 11th Avenue, Denver Colorado 80220. Telephone: (303) 331-4887. 
Colo. Rev. Stat 25-2113.5. 

UPDATE: Intermediary system available upon petition to the court for birth parents or siblings (court of termination) or adoptees (court of adoption) 21 and older (1989).