Colo. Rev. Stat. § 8-70-117
"Employment" means that the entire service of an individual is performed within this state or both within and without this state if the service is localized in this state; or that the service is not localized in any state but some of the service is performed in this state and that the base of operations or, if there is no base of operations, the place from which the service is directed or controlled is in this state; or that the base of operations or place from which the service is directed or controlled is not in any state in which some part of the service is performed but that the individual's residence is in this state. For purposes of this section, service shall be deemed to be localized within a state if the service is performed entirely within the state or if the service is performed both within and without the state but the service performed without the state is incidental to the individual's service within the state or, for example, is temporary or transitory in nature or consists of isolated transactions.
C.R.S. § 8-70-117