While there are no official rules regarding passport colors, countries do follow a certain set of norms when designing them. The International Civil Aviation Organization (ICAO), which works to define the principles of air travel, suggests that countries use a specific typeface, type size, and font for official documents like passports.
Granted, there are a few compulsory aspects of these international IDs. Passports are required to be made out of a material that bends in order to prevent creases, for instance. They also need to be read by a machine at temperatures ranging from 14 to 122°F, as well as at a relative air humidity ranging from five to 95 percent. But even if your passport meets all of the requirements, here’s why it could still be considered “expired” in some countries.
Despite the existing recommendations for these international documents, “nothing stipulates the cover color,” Anthony Philbin, ICAO’s chief communications officer, told Travel + Leisure. Passport shades aren’t just selected at random, though. Most countries still choose to use simple, dark shades of red, green, and blue. Why? Not only do dark colors look more official, but they can also hide dirt and wear.
However, there might be an even deeper meaning behind which of the four colors your home country chooses. Find out what your passport’s color really means.
[Source: Mental Floss]