The Coloured Tunnels are the centerpieces of the Depot. They start in the Depot and end all around Chuggington. Without them, Chuggington won't function properly and there will be a lot of chaos.
One of the more prominent episodes is Hodge and the Magnet. During the night, one of the track sections on the yellow line moved and wasn't inline with the other track section, which would cause an accident if a Chugger ran on it. Vee had to close the line and wait for Hodge to repair it. After some mishaps with Wilson, Hodge and the Magnet, the line was soon repair and Chuggington was back to normal.
During Hoot vs Toot, the tunnels were equipped with lights to show Hoot the right path to take when going down the red or the green tunnels. This is because it was found that Hoot is red-green colourbind as seen when he paints Wilson, green and mixes up a delivery of Tomatoes with a delivery of apples.