According to AutoEvolution, there is no definitive answer as to why police cars use red and blue lights. However, one of the most commonly seen answers is to make the lights easier to recognize for people who suffer from color blindness. People who suffer from red color-blindness can see the color blue and vice versa.
Police lights are fairly easy to notice, but authorities have faced criticism around the world for the strobe lights. Flashing lights, like those found on top of police cars, have been known to trigger seizures in people who suffer from photosensitive epilepsy. Police in Britain have prevented this by making their lights flash only five times per second, while many police vehicles around the world have lights that flash 10 times per second. Reducing this number by half makes the lights on top of police cars safe for roughly 95 percent of people who suffer from epilepsy.
Police have made many changes to their lights over time. In 1940, authorities used a beacon light on the top of their cars instead of the light bars that started to become popular in the early 1990s. Around this time, police also switched to using LED lights because they were more energy efficient than other flashing bulbs.