Cabin Atmosphere Control Systems High-pressure cylinders containing oxygen for aviation use can be identified by their a. green color and the words “BREATHING OXYGEN” stenciled in 1-inch white letters. b. yellow color and the words “AVIATOR’S BREATHING OXYGEN” stenciled in 1-inch white letters. c. green color and the words “AVIATOR’S BREATHING OXYGEN” stenciled in 1-inch white letters.