What can you do if you were wrongfully fired in Colorado?

Colorado is not a right-to-work state, therefore, presumably, you have some rights under state law regarding wrongful job actions. If your job was protected by a labor agreement, or contract you can contact your union representative for assistance. If not, there is a state agency which you can complain to and you can, of course, bring suit against your ex-employer for damages for the alleged "wrongful" termination.