Fire hydrants all provide water, so why do they come in different colors? The answer depends on where the hydrant is and which part of it you are looking at.
Rules vary between countries and cities. In Japan, Germany, Spain and the United Kingdom, many hydrants are below ground and covered by heavy metal plates. A nearby sign shows where to find them. In the United States, hydrants are often above ground beside a street or sidewalk.
The main body is usually painted a bright color, such as red, yellow or white. This makes it easier to see. The top and nozzle caps may use another color for a different reason. In some areas, that color tells firefighters about the hydrant's water flow.
The U.S. National Fire Protection Association uses four flow groups. A pale blue cap can mark the highest group, which supplies at least 1,500 gallons of water per minute. Green can mean 1,000 to 1,499 gallons per minute. Orange can mean 500 to 999, while red can mean less than 500.
These colors are not exactly the same everywhere. Local authorities may use different rules, so a red hydrant in one city may not mean the same thing in another. Still, the basic idea is simple: bright bodies help people find hydrants, while colored caps can quickly show how much water is available. The paint is not just decoration. It can carry useful information.