Oddly enough, depending on your point of view, Star Fleet uses old fashioned regulation departmental designation by color for uniforms. When I was in the U.S. Navy long ago we had just escaped the period where if you worked above deck you wore a white hat and if you worked below deck you wore a black hat (didn't show the grease and grime), and all the strips on the uniforms that showed rank were by color: Red for Engineering, White for Deck, Blue for Naval Command, etc.