Colo. Rev. Stat. § 39-2-110
To further improvement in appraisal and valuation procedures and methods and understanding and knowledge thereof, the division of property taxation shall conduct annual instruction and discussion sessions in the nature of a school for assessors, their employees, and employees of the division for periods not exceeding fifteen days in length. All costs of conducting such sessions shall be paid by the division, and the necessary travel and subsistence expenses of assessors and their employees while attending such sessions shall be paid by their respective counties. All assessors shall attend this annual school. Each assessor completing this school shall receive a certificate of achievement for his effort.
C.R.S. § 39-2-110
For the definition of "assessor", see § 39-1-102(2).