The most important signs on an airfield are which color?

• A. Red
• B. Black
• C. Yellow
• D. White

Answer: (A)

On airfields, color coding for signs communicates both the type of instruction and its urgency. Red signs carry mandatory instructions or prohibitions that must be followed to stay safe and to prevent entering restricted areas or conflicting with aircraft operations. Because these signs require immediate compliance, they are considered the most important. Think of red as the signal for actions you cannot ignore, such as stop or hold, which directly impact safety on runways and taxiways.

Yellow signs provide directional guidance and cautions; they help you navigate but don’t impose an absolute action you must take. Black signs with yellow lettering indicate location information, helping you know where you are on the airfield. White signs (where used) typically carry other instructions but do not carry the same level of mandatory prohibition as red signs.