Colo. Rev. Stat. § 15-15-102
No will or other testamentary disposition or testamentary provision of one of the owners in joint tenancy of real or personal property or of an interest in real or personal property shall destroy or affect the joint tenancy or prevent the entire title and interest owned by the joint tenants from becoming vested upon his death in the joint tenants who shall have survived him. Upon the death of an owner in joint tenancy of real or personal property or of an interest in real or personal property, leaving surviving him coowners under such joint tenancy, all of the interest and title which, immediately before such death was owned by all of the joint tenants under such joint tenancy, shall become vested in the survivors of such joint tenants in spite of and without regard to the provisions of a will of the joint tenant so dying or the admission to probate of such will and without regard to whether such will was executed before or after the creation of the joint tenancy.
C.R.S. § 15-15-102
This section is similar to former § 15-15-202 as it existed prior to 1990.