Regulation 39-22-103(8)(a). Resident individual. 
A resident individual means a natural person who is domiciled in Colorado. A resident individual can also be a natural person who maintains a fixed dwelling within Colorado and who spends in the aggregate more than six months of the taxable year within Colorado. If a person is domiciled in Colorado, that person remains a Colorado resident even though he or she temporarily resides outside of Colorado. Once a domicile is established, it will continue to determine a taxpayer’s residency until it has been abandoned as a domicile.