Everybody on an aircraft carrier deck has a role. Because it is a noisy dangerous and sometimes unforgiving place, each seaman typical has on a color coded top that distinguishes their roles.
White Tops – These are medical personnel, or they handle mail.
Red Tops – These are the guys who load or unload ordnance and fight fires. “Ordies”
Green Tops – These are the mechanics and deck ops personnel. Mostly maintain catapults and arresting gear
Yellow Tops – These are deck safety specialists, flight deck officers and they are typically launching the planes and moving them.
Checkered Shirts – Quality Control and flight readiness
Blue Tops – Deck crew, operate under purview of Yellow Tops
Brown Tops – These are the plane captains and the Chief Mechanics
Purple Tops – These are the fuel handlers.