Kolor Kut® Water Finding Paste offers a simple way to check for the presence of water in petroleum fluids such as gasoline, kerosene, diesel, and heavy fuel oil. Kolor Kut’s paste works by changing color (golden brown to red) once in contact with water. If you are testing for water in a tank, it is best to apply the Kolor Kut® to the measuring stick or rod you will be inserting into the tank. By “sticking” the rod or measuring stick into the tank you may also learn of the water depth in addition to its presence.