I was watching Deep Space 9 yesterday and on one of the episodes on the second disc of season 4, Worf is sitting in the captain's chair running the bridge with Kira and Jadzia behind him at the table talking and eating. Now at the Helm was a red shirt and at the sciences station there was another red shirt. Besides Word what are the other red shirts for in the Next Gen era? I cant figure out what position they would hold and what they would do.
Worf commented in passing that it felt good to be in a red uniform and that he was hoping he could do well in the command field (or something to that effect. either way he mentioned it was a command color.). That means in canon at least at that point and I am sure much earlier (probably in next gen) they established that red was for command personel only, by vocalizing it.
Now then I am not military man so I dont know how it is in the real navy but I would immagine there are lots of command positions but In star trek I can only see the need for three; captain, first officer, and second officer. All of the other positions seem to run and headed by people in that field/color uniform. For example the head of the Engineering department is a Gold Shirt the Chief Medical Officer is a blue shirt the Chief of Operations in multipul shows was a gold shirt and so was the Cheif of security, which means:
Red is reserved for only command personel
Gold is for Ship Operations
and Blue is for Sciences.
Now you might say duh everyone who knows star trek knows that. But then I re-ask my question what are all the other red shirts doing? Obviously it is not doing command level functions when the team leaders and department heads are all blue or gold shirts.