Colo. Rev. Stat. § 24-51-1742
If the deceased member had designated a beneficiary, other than the member's estate, to receive the refund of the accumulated contribution balance, no survivor's benefits shall be subject to claim under sections 24-51-1736 to 24-51-1746 unless such designated beneficiary or beneficiaries then entitled to receive such refund, by written notification delivered within such time and in such form as prescribed, shall elect, in lieu of receiving such refund, to have the provisions of sections 24-51-1736 to 24-51-1746 applied. If there is more than one designated beneficiary then entitled to receive such refund, such election must be joined in by all of them. If the deceased member had designated the estate as such beneficiary or if by operation of law the estate shall be entitled to such refund, then such election may be made by the duly appointed personal representative of the estate of such deceased member in like time and in like manner as may be prescribed by the board by general rule as specified in this section. If, however, such deceased member was qualified for retirement under the terms and conditions of sections 24-51-1713 and 24-51-1714, the designated beneficiary or beneficiaries so entitled to refund or benefits under sections 24-51-1736 to 24-51-1746, may elect, in lieu of such benefits, to allow benefits to be paid under either option B or option P3 subject to the applicable sections thereof providing for superannuation retirement. Such election shall be made within such time and in such form as the board may prescribe and shall become effective as of the day after the date of the member's death. If there is more than one designated beneficiary entitled to receive such benefits, such election must be joined in by all of them.
C.R.S. § 24-51-1742