C.R.S. § 11-56-113

(1) Except as otherwise provided in this article, all general obligation refunding bonds, refunding revenue bonds, and special obligation refunding bonds and the income therefrom shall be exempt from taxation, except inheritance, estate, and transfer taxes. (2) Bonds issued pursuant to this article for the purpose of refunding outstanding obligations which were neither exempt from such taxation at the time issued or at the time of the refunding nor which would have been exempt from such taxation if originally issued at the time of the refunding, shall be subject to taxation to the same extent and in the same manner as the outstanding obligations for the refunding of which they are issued.