A-4 API Color Symbols System
As to what colors are best for the various fuels sold, each customer can use their own scheme, but the recommendations of the American Petroleum Institute (API) are shown on the following chart. Anytime there is the slightest doubt as to color codes or what products that customer has: Stop and call dispatch.
SOURCE: dixonvalve.com
Industry Standard Color Codes
The API color code system is followed by bulk liquid petroleum marketing and storage facilities around the world. With some exceptions, most petroleum-based fuels look similar. Therefore, the API color code system was created to identify fuels and fluids and to prevent cross-contamination. Fuel storage tanks, piping, and equipment are painted with a color or combination of colors that correspond to the API chart to reflect what fuels are stored in the tank and/or what equipment can be used to load and unload the product.