Not all police cars are dark blue. In fact most are not. The ones you see that are dark blue are painted that color because that is the color chosen by that police dept.
no you dont
Chicago is famous for having only Blue lights on its police cars
Typically, the strobes are blue and red.
A dark blue, not quite as dark as the Midnight Blue some cars were painted back then.
When illuminated with white sunlight, a dark blue police car reflects mostly dark blue - which you see - and absorbs all the rest, such as red, green etc. It is similar with any object of some color. If the light comes from a sodium light which is mostly just yellow and some red, there is basically no blue to reflect from the car which, in the spectrum between red and blue, reflects only blue. Therefore the car will appear black or rather very dark and hard to see.
Most modern Italian Police cars are now pastal blue with a horizontal white stripe, prior to this they were white cars with a horizontal green stripe, earlier cars were all green.
To make the pretty blue and red lights higher and easier to see.
Emergency lights in state police cars in Indiana are blue and red in most counties in Indiana. These are common colours, not just in Indiana, but throughout the United States and the world!
The most popular colors for the Little Tikes cars are red and yellow, blue and black, and blue and green. Others include the police car (white and black) and red and black.