What are official postal guidelines identified with?

Official postal guidelines are identified with combinations of letters and numbers for several important reasons. This system allows for a unique and systematic way to categorize and identify various postal services, packages, and routes. By using both letters and numbers, it becomes easier to encode complex information in a way that can be quickly understood by both machines and humans involved in the postal process.

For example, postal codes often consist of letters and numbers that indicate specific geographical areas and sorting facilities. This format provides a structured way to ensure that mail is routed correctly and efficiently.

Using only numbers or only letters would limit the ability to create sufficiently unique identifiers that can accommodate the vast array of potential postal designations. Color coding, while useful in various contexts, does not inherently provide the same clarity and precision in conveying specific postal guidelines as the alphanumeric system does.