You can tell by the color of his robes.
Persian Gulf (Feb. 26, 2006) – Navy Chaplain, Lt. Kenneth Medve, reads the blessing of communion during Roman Catholic service in the foc’sle aboard the Nimitz-class aircraft carrier USS Ronald Reagan (CVN 76). Reagan and embarked Carrier Air Wing One Four (CVW-14) are currently deployed on her maiden deployment conducting Maritime Security Operations (MSO) in the region and participating in the global war on terrorism. U.S. Navy photo by Photographer’s Mate 3rd Class Dominique M. Lasco (RELEASED)
Every uniform on a carrier deck communicates that individual’s duties. Green is for maintenance crew. Red is for ordnance. Purple for fuel. Yellow is for aircraft handling officers and LSOs.
For more, see this.
(FOR THE RECORD: Yes, Murdoc is joking. Catholics, please no rioting in the streets!)