​​Why do Passports only come in Four Colors?

Red, green, blue and black are the shades that control the universe of passports and all of these have a good reason for it. There are some reasons to attribute to the choice of passport colors. The colors of the passports are limited, nations keep testing with the shades of these four main colors that may be attributed to "many possible scenarios."

Blue: Countries having blue colored passports are supposed to be the part of the so-called 'new-world' League of Nations. These nations are India, North America, South America and Australia among others.

Red: Red is supposed to be the color of the communist movement in all over the world. This color usually belongs to countries, which are known for having a communist history or still have its influence. Key examples of this type are China, Russia Serbia and Latvia.

Green: As per the Business Insider, religious faiths play a role in the color of the passport. This is the reason; Islamic nations like Saudi Arabia and Pakistan choose the different colors of green for their passport. Green is the color that Islam connects with Prophet Muhammad. Shades of green are also used in West African countries like Nigeria, Niger and Senegal, where it indicates their belonging to ECOWAS (the Economic Community of West African States)."

Black: Black is the most unique color used in a passport. One of the major nations to have black passports is New Zealand. The country chose this shade to be in sync with its national color. Other countries that also have black passport are mainly African countries, including Zambia and Angola.

It should be noticed that while the standard colors of passports are definitely four, but the shades and variations of these colors create hundred different shades. But it is not mandatory that all nations have the above mentioned reasons for having particular color on their passports. In fact, US has seemingly, tried all four colors for passports. The temporary passport of Canada is white in color. This is also an exception.