American Public Works Association color code for locator marks
Underground utility lines are marked with flags and/or paint in accordance with the color code below.
Facility markings show you only the approximate location of buried utility lines. Before you can safely work near a gas or electric line, you must first hand dig to expose the line and visually verify its exact location and depth. If you cannot visually verify the location of a marked utility line, STOP digging and call 811 immediately.