Colour Tanks were deployed during the Invasion of Raydian to collect Paint. The primary use of the Colour Tanks were to store all the colour and paint in Raydia and also used as a fast transport unit. Unlike it's counterpart, it does not have any arnaments to defend itself, and so, it is defenseless against enemies. Many were seen and deployed in the Hanging Gardens, Chroma City Fun Park and The Docklands.
The Colour Tanks do not have any power against you so you may use it to manipulate others around you. If you are in an area where there are Inky Mortars or somewhere a bit overwhelming, Colour Tanks can be used to destroy them.
If you a stuck in a single area, (depending on which level) Colour Tanks will be scouting the area and may come across you, use this time to destroy the Tank and counter the enemy. Colour Tanks are extremely useful if you are trying to get the 100% Colour Award.