For Khan and his followers, Robert Fletcher wanted to create a definite contrast with the Starfleet uniforms he had redesigned for Star Trek II.
His idea was that their clothes would be made out of whatever they could find on their spaceship, the Botany Bay, which had been abandoned by Kirk on Ceti Alpha V fifteen years earlier.
“My intention with Khan was to express the fact that they had been marooned on that planet with no technical infrastructure,” Fletcher recalled in an interview for the 2002 director’s edition release of the movie, “so they had to cannibalize from the spaceship whatever they used or wore.”
Therefore I tried to make it look as if they had dressed themselves out of pieces of upholstery and electrical equipment that composed the ship.
When it came to Ricardo Montalbán’s costume, there was another consideration: showing off the 61-year-old actor’s physique.
“He was rather proud of it,” said Fletcher, “as he should have been. That was a theatrical gesture.” The open-front costume even led to some speculation that Montalbán had worn a prosthetic chest for this scenes, which was not the case.
When Khan first appears, he is dressed from head to foot in rags. Again, Fletcher explained, the design was dictated by Khan’s situation:
They had to protect themselves from the planet, which was very inhospitable. That was the origin for the kind of Bedouin look. If you have nothing else, and you have access to some fabric you may have ripped out of a bedroom or whatever, then you wrap yourself up to protect yourself from the sandstorm.