Star Trek: What Ranks Do Each Color Shirt Represent?

gamerant.com:

Over the many years of thrivingStar Trek TV shows and movies, there has always been special attention shown towards the overall design of the science fiction genre defining franchise. Gene Roddenberry, the show's creator, even had a specific set of design rules for what the Federation ships were supposed to look like, ensuring that they would be instantly recognizable as Federation just from a quick glance. The importance of recognizable themes stayed strong, from the fairly logical design of the warp and transporter technology, all the way to what is potentially the most important visual aspect of the show: the costumes.

While there have been various changes made over the years (although, not as drastic a change as that of Klingon appearances), the Starfleet uniforms stay fairly similar. With the expedition of The Original Series, the colors used by the officers have stayed fairly consistent, each representing a different job aboard the ship. So what exactly do these colors mean?

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One of the most recognizable to anyone who is away from the age-old Star Trek joke about the poor officers who are donned in red. However, the idea that wearing a red shirt in the franchise is a death sentence is not only a myth, but is something that changed drastically after the official color changes occurred at the start of The Next Generation. In The Original Series, the red uniform was the most used aboard the ship, and was worn by those in engineering, security, and communications. The most notable of red wearing characters was chief engineer Scotty, and the groundbreaking Uhura (played by the late Nichelle Nichols).

After the uniform change made in TNG, the red shifted meaning.