The United Colors of Enterprise
In TOS, the crew’s uniform colors indicated their role on the Enterprise. Gold uniforms meant the person was on a command track. Blue meant the sciences, including medicine. And red indicated support services, like communications, engineering, or security.
Source: Deviant Art
Random fact: The only official intoxicant that was ever served in TNG’s Ten-Forward is Synthenol, which is artificial booze that loses its effects the moment a crew member leaves the bar. Can you imagine if that existed in the real world?