These mauve-colored costumes were long a mystery, since no uniforms on Star Trek: The Original Series had this unusual color. Some speculated that they might have been unused prototypes for cadet uniforms or that they might have been intended for use if the original series had gone to a fourth season. The real answer proved equally intriguing. Recent comparison of these mauve costumes to fabric samples from the same time period has demonstrated that identically-dyed blue cloth can, indeed, fade to this mauve color. In other words, these costumes were once the same color as Spock's blue shirts, and they were indeed made for the Star Trek pilot episodes.