A green shirt
is a colloquial term for technicians who work on flight decks in the US Navy
When a technician is required, the pilot indicates which specialty is needed using the ADMOT signal. The LSO then directs the tech safely to the aircraft when approved by the pilot. The technician will correct the discrepancy and the flight would resume.
Normally, green shirts would wear green flotation vests in the event they fell overboard. A gaggle of green shirts can be seen at the end of the movie Top Gun, surrounding Tom Cruise’s character and jockeying to be in the shot.