this is from the FAA website
http://www.faa.gov/airports_airtraffic/air...150_5210_5c.pdf
VEHICLE PAINTING.
a.
Ambulances. Ambulance vehicles are painted per Federal Specification KKK-A-1822E, Federal Specification for the Star-of-Life Ambulance.
b.
Aircraft Rescue and Firefighting (ARFF) Vehicles. Yellowish-green is the vehicle color standard. Color specifications are per Appendix A.
NOTE: A yellowish-green color provides optimum visibility during all light levels encountered during a 24-hour day and under variations of light that result from weather and seasonal changes.
c.
Airport Operations Vehicles, Airfield Service Vehicles. Chrome yellow is the vehicle color standard. Color specifications are per Appendix A. When vehicles are equipped with bumper bars 8 inches (205mm) or more in depth, the bars should be painted in alternate stripes 4 inches (100mm) in width of chrome yellow and black inclined 45° to the vertical.
d.
Aircraft Support Vehicles and Other Vehicles. Any color or combination of colors other than yellowish-green or chrome yellow. The bumper bar markings in paragraph 3c are recommended.
e.
Airport Security Vehicles. Comply with specific state or local requirements.