What color combination represents mandatory airport signs?

• A. White on red.
• B. Yellow on black.
• C. Black on yellow.
• D. White on blue.

Answer: (A)

Mandatory signs on airports use a red background with white lettering. That combination is chosen because it clearly signals actions that must be followed for safety, such as holding short of a runway or not entering a restricted area. The bright red background stands out, and the white text remains highly legible, making the command unmistakable even in cluttered or low-visibility conditions. Other color schemes are used for information, directions, or caution, not for mandatory instructions, so they don’t convey the same obligation to act.