Which background color is used for mandatory instruction signs in aerodromes?

Mandatory instruction signs at aerodromes are characterized by a background color of red. This color choice is significant because it grabs attention and conveys important information that requires immediate compliance from pilots and ground personnel. Mandatory instruction signs typically convey rules that must be followed, such as "Hold Short" or "No Entry," which are critical for ensuring safety on the airport surface.

Red is universally associated with warnings and prohibitions, making it an effective choice for conveying mandatory instructions that need to be observed without exception. The high visibility of red also helps to prevent accidents and misunderstandings in busy airport environments where clear communication is essential for safe operations. Other colors, such as green for guidance signs, white for informational signs, and blue for service signs, serve different purposes and indicate other types of messages, but red is distinctively used for mandatory instructions.