C.R.S. § 18-1-504

(1) A person is not relieved of criminal liability for conduct because he engaged in that conduct under a mistaken belief of fact, unless: (a) It negatives the existence of a particular mental state essential to commission of the offense; or (b) The statute defining the offense or a statute relating thereto expressly provides that a factual mistake or the mental state resulting therefrom constitutes a defense or exemption; or (c) The factual mistake or the mental state resulting therefrom is of a kind that supports a defense of justification as defined in sections 18-1-701 to 18-1-707 . (2) A person is not relieved of criminal liability for conduct because he engages in that conduct under a mistaken belief that it does not, as a matter of law, constitute an offense, unless the conduct is permitted by one or more of the following: (a) A statute or ordinance binding in this state; (b) An administrative regulation, order, or grant of permission by a body or official authorized and empowered to make such order or grant the permission under the laws of the state of Colorado; (c) An official written interpretation of the statute or law relating to the offense, made or issued by a public servant, agency, or body legally charged or empowered with the responsibility of administering, enforcing, or interpreting a statute, ordinance, regulation, order, or law. If such interpretation is by judicial decision, it must be binding in the state of Colorado. (3) Any defense authorized by this section is an affirmative defense.