The Kraton name belongs to Kraton Performance Polymers, Incorporated, and the Kray-Ex name is trademarked by Cold Steel, so Cold Steel would not simply have used the same material but changed the name. It would be the equivalent of re-boxing Kleenex tissues and re-branding them Klear-Tex, while going to the trouble of trademarking the Klear-Tex name. What would be the point in that, particularly if you're not a manufacturer of tissues?
I suspect that Kray-Ex, like Carbon V, is Cold Steel's proprietary variation on/enhancement of a preexisting material. Since Cold Steel pioneered the use of Kraton as a knife handle material, through the decades they must have felt that it could stand some improvement, thus the creation of Kray-Ex. I'm guessing that Kray-Ex probably has better resistance to heat and chemicals (such as DEET), both of which were drawbacks of Kraton (though performance improvements were also made to Kraton over the years).
Here you go, mastiffhound: A rare, entirely sterile, American-made Trail Master in Carbon V, brass, and Kraton, purchased directly from Cold Steel as a Second many years ago (fault is a very slight deformation of the guard, barely noticable and wholly insignificant for performance).
-Steve