It turns out that there are only four primary passport colors in the world, and each country has its own reasons for choosing one of these colors for the cover.
This is the most common color. Passports with a red cover are often chosen by countries with a historical or current communist system. Citizens of Slovenia, China, Serbia, Russia, Latvia, Romania, Poland, and Georgia have red passports. Member countries of the European Union, except Croatia, also use passports of burgundy and other shades of red. Countries interested in joining the EU, such as Turkey, Macedonia, and Albania, changed the color of their passports to red a few years ago. The Andean Community of Nations — Bolivia, Colombia, Ecuador, and Peru — also has burgundy passports.
This is the next most common color. The blue cover symbolizes the “new world”. 15 Caribbean countries have blue passports. Within the block of South American countries, the blue passport cover symbolizes the connection with Mercosur — a trade union. This includes Brazil, Argentina, and Paraguay. Venezuela is the exception here: it also belongs to the union, but its citizens have red passports. The passports of US citizens were changed to blue only in 1976.
Most Muslim countries have green passports. Examples include Morocco, Saudi Arabia, and Pakistan. Green is considered to be the favorite color of the Prophet Muhammad and is a symbol of nature and life. The citizens of several West African countries — for example, Burkina Faso, Nigeria, Niger, the Ivory Coast, and Senegal — also have travel documents that are various shades of green. In their case, the color indicates that they belong to ECOWAS (the Economic Community of West African States).
The rarest passports are those with black covers. These can be found among the citizens of some African countries — Botswana, Zambia, Burundi, Gabon, Angola, Chad, Congo, Malawi and others. Citizens of New Zealand also have black passport covers, because black is the country’s national color.