The international color code used by utility locators to mark an underground gas line is?

• A. Orange
• B. Red
• C. Blue
• D. Yellow

Answer: (D)

Color-coded markings tell crews what lies beneath before digging, so everyone can work safely. For underground gas lines, yellow marks are used because yellow signals a warning about flammable gas, helping distinguish gas from other utilities and reducing the risk of damage or leaks during excavation. Other colors map to different services—red for electric power, blue for potable water, green for sewer—so the color system quickly communicates what’s underground. While regional differences can exist, yellow is widely recognized as the standard color for gas lines.