Which of the following colors would be inappropriate for a mandatory instruction sign?

Mandatory instruction signs are crucial for ensuring safe operations at airports by providing pilots with essential information regarding restrictions or instructions that must be followed. The standards for these signs are established by aviation regulatory authorities, and they typically use specific colors to convey their intended messages effectively.

The color used for mandatory instruction signs is primarily red. Red signifies that the instruction must be adhered to without exception. Therefore, when assessing appropriate colors for these signs, we focus on those that communicate clear and mandatory directives.

Orange is typically associated with warning signs, indicating caution or providing information about possible hazards rather than mandatory actions. Consequently, orange would not be appropriate for conveying mandatory instructions in the aviation context.

White is generally used for information signs, offering useful but non-mandatory information, while blue is used for services available to pilots, such as fuel or maintenance information.

By understanding the specific use of colors in aviation signage, it becomes clear that orange does not align with the established color coding for mandatory instruction signs and is, therefore, not appropriate.