Why fire engines are red

WHY ARE FIRE ENGINES RED?
Books are red too;
Two and two are four;
Four times three is twelve;
There are twelve inches in a ruler;
Queen Elizabeth is a ruler;
Queen Elizabeth was also a ship;
Ships sail across the sea;
The sea is full of fish;
Fish have fins;
The Finns fought the Russians;
The Russians were Red;
Fire engines are always rushin'...
...And THAT'S why fire engines are red!