There are several theories about why fire engines are red. One theory suggests that fire trucks were first painted red back in the 1800s when fire brigades took so much pride in their trucks that they wanted them to stand out and feature the most regal and expensive color, which at the time was red.
Others believe fire trucks were first painted red because of early cars. When the automobile was first made by Henry Ford, they were all black because it was an inexpensive color. With so many black automobiles on the road, the fire brigades wanted the trucks to stand out, so they painted them red.