Colo. Rev. Stat. § 37-23-102
The board of directors shall cause to be personally served upon all parties residing in the district and owning land to be affected by the proposed drainage system, or other property liable to be taxed, a written or printed notice of the time when, and place where, it will meet to hear any objections that may be made to classifications of lands on the graduated scale. The notice shall be served in case of residence in the district not less than three days before the time set for hearing, by delivering a copy thereof to the party to be served. In the event that such copy cannot be personally delivered to the party to be served, then such notice shall be served in the manner provided for the service of summons in the Colorado rules of civil procedure. The board of directors shall cause to be sent by mail, at least ten days before the time set for said hearing, such notice to all owners who do not reside in the district whose land is affected, in case their post-office address is known to the board of directors or can be ascertained by the use of reasonable diligence. In case the land of any nonresident or of anyone whose residence is unknown is affected, then publication shall be made in some newspaper published in said county for three successive weeks prior to the time of such hearing, the publication to be made after a resolution of the board of directors has been duly passed determining the names of those landowners within the district who are nonresidents of the state or whose residence is unknown, and such meeting to hear objections may be adjourned from day to day by public announcement of the board of directors made at the meeting, until all objections are heard. All persons duly notified of the first day of meeting shall take cognizance of all adjournments without further notice. The affidavit of any creditable person that he has posted or served the notice required and the certificate of the publishers of such newspaper as to such publication shall be sufficient evidence of such facts.
C.R.S. § 37-23-102
For service of process, see C.R.C.P. 4; for publication of legal notices, see part 1 of article 70 of title 24 .