What is the primary color scheme for mandatory instruction signs?

Mandatory instruction signs in aviation are designed to convey crucial information pertaining to regulations and actions that must be followed by pilots. The standard for these signs is white text on a red background. This color scheme is intentionally chosen for its visibility and to draw attention, ensuring that pilots are aware of important instructions such as "Do Not Enter" or "Hold Position."

The use of red as the background color is particularly significant because red universally signifies caution, prohibition, or mandatory action, aligning with the need for pilots to adhere strictly to these directives. The contrast of white text against this bold red background enhances readability and quick recognition, which is critical in a fast-paced environment like an airport.

Other color schemes, such as yellow on blue, red on white, or green on black, serve different purposes in the aviation signage context. For instance, yellow typically indicates cautionary information, while green is often used for informational signs, none of which convey the mandatory nature of compliance like white text on red does.