What Do All Those Colors Mean?

The American Public Works Association has developed a color code for marking underground utilities across the United States. This standard keeps us all on the same page and makes the world a little bit safer for everyone.

The most common colors people might encounter are orange, red, yellow, and blue.

Orange-painted lines on the ground represent communications lines such as fiber optic telephone or broadband internet cables, but they can also include cables carrying traffic, railroad, or other signaling information.

Red paint indicates the presence of underground electrical wires. A red mark on the ground can represent electrical power, ranging from low-voltage decorative lighting to high-voltage distribution systems. You should use extreme caution when digging around any facilities painted or flagged near your work area.

Yellow is used to designate petroleum products in either liquid or gaseous form and pressurized steam pipelines. Natural gas and propane are the two most common gases in residential and commercial settings today. Cross-country petroleum transmission pipelines are also usually marked in this color. Defacing temporary or permanent pipeline markings is a felony.

Potable or drinking water is marked with blue paint or flags. This includes the water mains delivering municipal water to your home or business and water from wells used for human consumption.

Purple marks mean the water in the pipe below has been reclaimed. Reclaimed water is unfit for human consumption.

Green paint indicates the presence of underground sewage pipes. Pressurized sewer pipes are called forced mains. These systems depend on mechanical pressure to move wastewater from one place to another rather than gravity. You do not want to be present if a forced sewer main ruptures.

The final three elements of the APWA color code are pink, purple, and white. White paint should be reserved only for marking proposed excavation routes or areas. Using white paint, flags, or stakes to designate where you intend to dig before you call 811 is very helpful to utility locating technicians.

Pink paint is used for temporary survey markings and may indicate anything from an underground utility to a surveyor’s reference point. I often use pink paint to mark utilities I cannot otherwise identify.

Any lines painted or flagged should always be treated as an unknown until you have physically verified the utility or utilities beneath the surface by visual inspection. Professional locators do their best to provide accurate information to those who utilize our work, but we’d rather mislabel a facility than leave it unmarked.

Please visit the American Public Works Association or Common Ground Alliance for more information.