Originally Posted by John Ridley
My brother's a firefighter/paramedic. He said the switch to green trucks (because of higher visibility than red) has somewhat reversed because the crazy light & sound packs that are now required render the color of the truck a bit of a moot point. He also said that they'd discovered that a certain shade of violently hot pink is even more visible than green, but to date he has not seen any hot pink fire trucks :-)
My old psych professor told me that while green was easier spotted, red was used because people subconsciously associated that with an emergency vehicle while green didn't have that association. Plus nowadays you can see and hear them before you can make out what color they are.