Utility Marking Colors Explained: What Red, Yellow, Orange, Blue, Green, Purple, Pink and White Mean

Locate marks follow a national colour code set by the American Public Works Association. The same colours mean the same thing in every state, so once you know them you can read a marked site anywhere. Marks are usually paint on hard surfaces and flags on soil, and both use the same colours.

Red — Electric

Electric power lines, cables, conduit and lighting cables. Treat red as the most dangerous colour on any site. Primary distribution can carry many thousands of volts and does not need to be touched to injure you — an arc can jump. Red also covers street lighting and traffic signal circuits, which people often assume are low voltage and are not always.

Yellow — Gas, oil, steam and petroleum

Natural gas, oil, steam, petroleum and other flammable or explosive material. Yellow and red are the two you stop for. A struck gas line is an evacuate-and-call-911 situation, not something to assess yourself. High pressure transmission lines can be in the same trench as a service line and look no different on the surface.

Orange — Communications

Telephone, cable TV, fibre optic, alarm and signal lines, and the conduit that carries them. Orange lines rarely hurt you, but fibre is expensive and cutting a trunk line can take out service for a whole area. Orange is the most common colour on residential sites because so much of it has been added over the years.

Blue — Potable water

Drinking water mains and services. Blue can be deep or surprisingly shallow depending on frost line and when it was installed. Older blue lines may be galvanised, cast iron, copper or asbestos cement, and the material affects how easily they can be located and how they fail when struck.

Green — Sewer and drain

Sanitary sewer, storm drain, and the associated culverts. Green lines are usually gravity fed, which means they sit at a consistent slope rather than a consistent depth. Many are non-conductive clay, concrete or PVC and cannot be found electromagnetically at all — they need a sonde, a camera, or ground penetrating radar.

Purple — Reclaimed water, irrigation and slurry

Reclaimed or recycled water, irrigation lines and slurry lines. Purple is becoming more common as municipalities expand reclaimed water systems. It is easy to confuse with blue at a glance on a faded mark, which matters because the two carry very different water.

Pink — Temporary survey markings

Temporary survey markings, unknown or unidentified facilities. Pink is the colour to pay attention to. It often means a locator found a signal but could not confirm what the line was. Pink means uncertainty, not safety — treat anything pink as though it could be any of the above until proven otherwise.

White — Proposed excavation

The excavation area itself, marked by the excavator before the locate. White-lining tells the locator exactly where you plan to dig so they mark the right area rather than the whole property. Washington, Oregon and Idaho all require or expect pre-marking in white. Doing it properly gets you a better locate and fewer return visits.

What the marks do not tell you

Colour tells you what a line carries. It does not tell you depth, and no locate should be treated as a depth measurement. Marks also drift: paint fades, flags get pulled, and grading moves everything. If marks are disturbed or weathered, request a re-mark rather than guessing. Maintaining the marks once they are down is the excavator's responsibility.

Marks only cover what the operator owns. 811 locates stop at the meter. Anything past that point — electrical to a shop or barn, irrigation, gas to a pool heater, septic lines, private water — is the property owner's and stays unmarked unless it is located privately.

Get the private lines located

Advanced Underground Utility Locating Inc locates private utilities across Washington, Oregon, Idaho, Montana and northern California, using electromagnetic locating and ground penetrating radar. Spokane and Eastern Washington: 509-710-2621. Seattle, Tacoma and Portland: 509-954-8623. Bend and Medford: 541-678-0629. Eugene and Roseburg: 541-780-4149. Coos Bay and the Oregon Coast: 541-315-6728. Emergency service is available 24 hours.

Colour code per the American Public Works Association uniform colour code, used nationally under the standard adopted by the Common Ground Alliance.