Stand on the bridge wing of an American aircraft carrier during flight operations and the deck below looks like a paint chart having a nervous breakdown. Yellow, green, red, purple, blue, brown and white, all moving at once, in a space the size of three football pitches with jet engines running on it.

It is not decoration and it is not squadron pride. It is the reason the deck works at all.

Nobody on a flight deck can hear anything. Radios are for the people who need them; everyone else communicates by hand signal and by knowing, at a glance and at distance, exactly what the person walking towards them is allowed to do. The colour of a jersey is a job title you can read at fifty metres through jet blast.

The Whole System in One Sentence

Note the three items. It is not just the shirt. The float coat — the inflatable life preserver everyone wears — matches, and so does the cranial, the padded helmet with the ear defenders. Whichever way someone is facing, and whether they are standing up or crouched under a wing, the colour reads.

Yellow: The Ones Everybody Watches

Yellow is authority over aircraft movement. The aircraft handling officer, the catapult and arresting gear officer, and the plane directors all wear it.

A yellowshirt directing an aircraft has absolute control of that aircraft for as long as the pilot is looking at them, and the handover from one yellowshirt to the next as a jet moves up the deck is a deliberate, visible ritual. Pilots follow the signals of exactly one person at a time, and the colour is how they know which one.

On deck they get called bears.

Green: The Machinery

Green covers the largest and least glamorous list on the deck. Catapult and arresting gear crews are green. So are air wing maintainers and quality controllers, cargo handlers, ground support equipment troubleshooters, hook runners, the visual landing aid electricians who keep the optical landing system honest, photographer’s mates, and the helicopter landing signal enlisted personnel.

If something on the deck is a machine and it has to work, somebody in green is responsible for it.

Red: Things That Go Wrong, and Things That Go Bang

Red is worn by ordnance handlers — the ordies, who load the weapons — and also by the crash and salvage crew, explosive ordnance disposal, and the firefighting and damage control party.

It is a sensible pairing. The two situations in which you most need to identify someone instantly from across a crowded deck are a weapons movement and a fire.

Purple: The Grapes

Purple belongs to the aviation fuel handlers, and the nickname is universal and affectionate: grapes. They run the hoses, they know exactly how much is in each aircraft, and everybody else on deck gives them room.

Blue: Where You Start

Blue is the entry point. Trainee plane handlers, the chocks-and-chains teams who secure aircraft, aircraft elevator operators, tractor drivers, messengers and phone talkers all wear blue, and they work under the yellowshirts.

Almost everyone who ends up in another colour started in this one.

Brown: Somebody Owns That Aeroplane

Brown is worn by air wing plane captains and air wing line leading petty officers. A plane captain is responsible for a specific aircraft — preparing it, checking it, handing it to the pilot and taking it back.

It is a young person’s job with an enormous amount of ownership attached to it, and the brown shirt is how a pilot finds the right one in a deck full of people.

White: The Ones Watching Everybody Else

White is for quality assurance, squadron plane inspectors, air transfer officers, liquid oxygen crews, safety observers, medical personnel — who wear a red cross on the white — and the landing signal officer.

The LSO is the person standing at the aft port corner of the deck talking landing aircraft down, and the fact that the job sits in the same colour band as the safety observers tells you how the Navy thinks about it.

Why It Has To Be Colour

Every other identification method fails on a flight deck. Names are unreadable. Rank insignia are unreadable. Voices do not carry. The people involved are wearing goggles, ear defenders and bulky protective gear that hides everything except their outline.

What survives all of that is a large block of saturated colour, visible in daylight, visible under floodlights at night, and visible from the tower, the LSO platform, the cockpit of a taxiing Super Hornet and the deck itself at the same time.

The system is old, low-tech and slightly absurd to look at. It is also one of the more elegant pieces of safety engineering in aviation, and it has outlasted every technology that has been proposed to replace it.

Sources: Wikipedia (Modern United States Navy carrier air operations); U.S. Navy imagery.