For the people who have them, a passport is a document that entitles you to live in and travel through various countries. Some passports are more powerful than others, but all grant you some kind of rights and privileges based on your citizenship.

Because of this, these documents hold both importance to the people who hold them. But for many people in Britain at the moment, a more superficial aspect of the passport has become a topic of national debate: its color.

Last week, Britain's Home Office announced that the British government is planning to spend £490 million (roughly $610 million) on a redesign of its passports. Politicians and right-wing tabloids such as the Sun are making one big demand of any new document — the color of the passport's cover should be changed from its current deep burgundy to a dark blue.

If the color of the passport is changed, it won't be just a cosmetic change. It'll also be symbolic. From 1920 until 1988, the British passport was blue. The burgundy document was introduced in 1988 as the country adopted machine-readable passports. These passports followed a common format that had been agreed upon by members of what was then the European Community and now the European Union.

One key marker of an E.U. member state's passport is that it is generally burgundy, although some countries prefer to choose their own color (Croatia's is blue, for example). Exactly why maroon was chosen by the E.C. is not entirely clear, but it did take member states many years to agree on the precise hue. It's a little symbolic measure that those who know about passports make note of: Turkey actually changed its passport to burgundy in 2010 in anticipation of eventually joining the E.U.

Now that Britain is marching toward its post-E.U. future, some view the current burgundy passport as an affront and a reminder of its decades of servitude to Brussels. Weeks after last summer's Brexit vote, the Sun began its campaign to have the blue passport brought back, while Member of Parliament Andrew Rosindell said it was a “humiliation” that Britons were forced to have a “pink” E.U. passport.

“National identity matters and there is no better way of demonstrating this today than by bringing back this much-loved national symbol when traveling overseas,” the Conservative politician said in an interview with Britain's Press Association over the weekend. Rosindell cited the example of the Swiss and Americans, who hold bright red and dark blue passports respectively, as examples of people who can “feel pride and self-confidence in their own nationality when traveling.”

The Home Office hasn't said whether it will change the color of the passport yet, noting that the planned redesign was not a response to Britain's vote to leave the E.U. and that the country redesigns its passports every five years anyway. However, the idea that the passport could be changed back to blue has struck many Britons as a pointless move: Few citizens under 30 are likely able to remember the old passports anyway.

“Changing the color of the passport is just another expense on an ever-increasing list of the cost of Brexit,” Tim Farron, leader of the pro-E.U. Liberal Democrats, said over the weekend.

Changing the color of a nation's passport isn't totally unusual, of course. The Economist notes that in the 20th century, the United States changed its passport color from beige to green to red to green again before finally settling on blue in 1976. And there is some logic to the idea that the color of your passport really does say something about your country.

The passport tracking website Passport Index lists 59 passports with red covers, which includes the E.U. burgundy passports but also Russia and a number of Asian countries with their own shades of the color. A further 77 have blue passports, including much of the Americas, the Caribbean and also a large number of African nations. Forty-two countries have green passports; many are majority-Muslim countries, which may have chosen the color as it is said to have been the prophet Muhammad's favorite color.

A smaller group of 10 countries have black passports. These are largely African nations, although New Zealand also has a black cover, which was introduced in 2009.

As such, perhaps you could argue that a British move to a blue passport would show that the country was looking toward transatlantic relationships over its previous ties with Europe. However, such a move would be entirely symbolic. In fact, one of the few practical benefits of changing color would be that anyone holding the blue passport in an E.U.-nationals line at immigration control could be advised to enter the line for other passport holders.

That itself is an indication of the real effect of Brexit on Britain's passport. Arton Capital, a financial firm that runs the Passport Index, once ranked the British passport as jointly the third most powerful in the world. However, the firm has warned that once Britain leaves the E.U., it could drop to 26th place, just behind Mexico, unless new agreements are reached.

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