"If you notice the tabs at the shoulders they are new also. They are a device which tells by color what a person's job or designation onboard ship is. For example, gold for security, green for medical, etc. Gene [Roddenberry] felt it was more important to indicate a person's job rather than his rank."
I like the idea of the shoulder rank in TMP, but it was pretty hard to see except at close range, something a little larger would be more useful.
costume designer Robert Fletcher as interviewed in Fantastic Films