Ever the showman, here Presley takes advantage of the herd trend in karate at the time. Upon general observation, he is clearly holding some sort of hardened surface underneath his gi when 'absorbing' a strike, to the sloppy made-up movements lacking technique, & the overall 'cocky' attitude is unbecoming a disciplined master of the art.
The legendary & elusive "scarlet belt" is spoken of from time to time in various dojos, particularly that in Kenpo & Kung Fu, which is essentially a silken sash rather than the typical cloth. However, these particular 'demonstrations' are absolutely most basic, & clearly appear to be actually for entertainment purposes. They are rather amusing, nonetheless. It is hardly likely that Elvis Presley ever genuinely possessed one; besides, "Sensei Presley" doesn't exactly have a ring to it, & there is apparently plenty of reason why.