C.R.S. § 4-3-205

(a) If an indorsement is made by the holder of an instrument, whether payable to an identified person or payable to bearer, and the indorsement identifies a person to whom it makes the instrument payable, it is a “special indorsement.” When specially indorsed, an instrument becomes payable to the identified person and may be negotiated only by the indorsement of that person. The principles stated in section 4-3-110 apply to special indorsements. (b) If an indorsement is made by the holder of an instrument and it is not a special indorsement, it is a “blank indorsement.” When indorsed in blank, an instrument becomes payable to bearer and may be negotiated by transfer of possession alone until specially indorsed. (c) The holder may convert a blank indorsement that consists only of a signature into a special indorsement by writing, above the signature of the indorser, words identifying the person to whom the instrument is made payable. (d) “Anomalous indorsement” means an indorsement made by a person who is not the holder of the instrument. An anomalous indorsement does not affect the manner in which the instrument may be negotiated.