Colo. Rev. Stat. § 8-3-117
Nothing in this article shall operate to abrogate, annul, or modify any valid agreement respecting employment relations existing on or before April 1, 1943.
Source: L. 43: p. 411, § 15. CSA: C. 97, § 94(15). CRS 53: § 80-5-15. C.R.S. 1963: § 80-4-15.