Command officers wear gold uniforms in the original series of Star Trek.
The color identifies Starfleet’s Command Division, which includes personnel responsible for command, helm, and navigation duties. Captain James T. Kirk’s familiar tunic is the best-known example, while officers such as Mr. Spock and Lieutenant Uhura also wear command-colored uniforms when assigned to those functions.
The color can be confusing because many original-series command tunics were actually made in a yellow-green or chartreuse fabric. Studio lighting, film processing, and later restoration made them appear strongly yellow or gold on screen. The production design nevertheless established gold as the recognizable command color, alongside red for engineering, operations, and security, and blue for science and medical staff.
This scheme is specific to the original series era. Later Star Trek productions changed the department-color system: The Next Generation, for example, uses red for command and helm. That is why remembering later captains’ uniforms can lead to the wrong answer for Kirk’s crew.