If each passport is different depending on their country, did you know that there are only four different passport colours? We'll explain to you what these four colours correspond to and which countries they refer to.Is your passport red? This is normal; it is the most common colour in Europe. But did you know why? In fact, it refers to... the communist system. It was the one adopted by the European Union.The blue passport represents the new world - that is, the United States and a large part of the South American nations. As for Muslim countries, they use a green passport, which might have been the Prophet's favourite colour.And finally, to finish, the fourth and last passport, the black passport, is used in African countries... but also in New Zealand.Now, just by seeing the colour of other passengers' passports on board your plane, you will know in which part of the globe their country is without having to read the name on the cover.