United Kingdom British Passport : Series 1
It is a myth that the dark blue colour is uniquely British and a national icon - the League of Nations gave member states a choice between blue, red, green and black, and the UK opted for blue. Or was it navy blue? Or black?

Prior to 1920, British passports consisted of a single sheet of card. In 1920, the League of Nations organised the Conference on Passports, Customs Formalities and Through Tickets in Paris. The resolution of this conference, passed on 21 October 1920, imposed a new set of standards that passports would have to meet to be internationally recognised.

The League of Nations ruling required that the passport be a booklet of 32 pages, with the dimensions 15.5cm x 10.5cm. It specified the information that the passport must contain, and the format it should be presented in. And it demanded that all passports be written in French, in addition to the national language of the issuing state. Today, ICAO standards require that passports must provide the information in English, French or Spanish. However, they specify that when the national language of the issuing state is English, French or Spanish, the passport should use one of the other two languages as well. After Brexit, the UK could decide to switch the second language of our passports from French to Spanish, but it could not eliminate the second language altogether, notwithstanding the fact that English is now the global lingua franca.

LEAGUE OF NATIONS RECOMMENDATIONS

On 21 October 1920, the League of Nations convened in France for a meeting that would shape modern travel.

After World War I, easing border crossings by train was a priority, but the lack of a standardized passport design posed "a serious obstacle to the resumption of normal intercourse and to the economic recovery of the world," the League noted. Border officials struggled to scrutinize foreign certifications of dizzying shapes and sizes, with sometimes partial information and little guidance as to what was authentic.

The Paris Conference on Passports & Customs Formalities and Through Tickets specified the size, layout, and design of travel documents for 42 nations. It ratified the template for a 32-page booklet exactly 15.5 × 10.5 cm (6.1 × 4.1 inches) with the first four pages detailing the bearer’s facial characteristics, occupation, and residence.

Assuming that travelers were married males traveling with their families, the layout included a box for a photo of the bearer's spouse and space for the names of his children. Each passport was to be in French and at least one other language; its cardboard cover would have the country's name and coat of arms centered on it; and the document should cost no more than 10 francs.