Why is the US Navy Red Book call that if it isn't red?

The US Navy's "Red Book" is informally named for its significance rather than its color, as it often features a red cover or is associated with important naval operations and policies. The term "red" signifies urgency and importance, akin to how red is used in various contexts to denote critical information. Additionally, the title reflects its status as a key reference document for naval personnel, emphasizing its role in guiding operations and decision-making.