Colo. Rev. Stat. § 10-3-203
Any domestic insurance company depositing its insurance reserves with the commissioner under the optional reserve deposit law, section 10-7-101, at its option and in addition to its insurance reserves deposit, may also deposit with the commissioner approved securities not less in amount than the reserve required to mature any or all of the company's other contractual obligations of every kind designated at the time the deposits are made. Such additional deposits shall be to secure the payment of such other contractual obligations so designated. In determining the amount of deposit to be maintained with the commissioner on account of insurance or other reserves, he shall make proper deductions from the mathematical reserves for all indebtedness to the company on account of each policy and each contractual obligation not exceeding the reserve thereon, and for deferred and uncollected premiums on the policies and for the reserve on such part of each policy as may be reinsured as provided by law. Any amount at any time on deposit in excess of the amount required may be withdrawn by the depositing company. Whenever any such company makes an application to withdraw any excess deposit, the commissioner may accept the estimate or calculation of the company of such reserves or, at his option, may have a calculation or estimate thereof made for said purpose or an appraisal of the depositing company's securities, or both, at the expense of the company so applying, at such reasonable expense as may be agreed to by the company.
C.R.S. § 10-3-203