Colo. Rev. Stat. § 8-70-134
"Employment" does not include services with respect to which unemployment compensation is payable under an unemployment compensation system established by an act of congress. The division is authorized to enter into agreements with the proper agencies under such act of congress, which agreements shall become effective ten days after publication thereof in the manner provided in section 8-72-102 for general rules, to provide reciprocal treatment to individuals who have, after acquiring potential rights to benefits under articles 70 to 82 of this title, acquired rights to unemployment compensation under such act of congress or who have, after acquiring potential rights to unemployment compensation under such act of congress, acquired rights to benefits under articles 70 to 82 of this title.
C.R.S. § 8-70-134