Sometime around the year 2000, municipalities in the region decided to colour code hydrants so that fire firefighters would know the water pressure available from each hydrant. FOR THIS REASON YOU SHOULD NEVER PAINT A HYDRANT - No matter how cool it looks as a minion, or as a dog!
You can read below for more information.
What the colour of fire hydrant top (or bib) tells you:
BLUE = water flow of >95 litres per second
GREEN = between 63 and 95 litres per second
YELLOW = between 31 and 63 litres per second
RED = less than 31 litres a second
A hydrant’s water flow depends on the available pressure, and the size and condition of the water line.
While water pressure typically depends on elevation, other factors can affect the flow.
The highest water pressure can be near flowing water, like a river.
But in areas where old cast iron lines deliver the water, the flow is less because they rust inside and restrict the flow.
Municipalities are required to colour-code all hydrants but have a variety of options.
While many cities paint hydrant tops, other attach coloured reflectors which firefighters say are highly visible during snowstorms or at night time when it is harder to find them