United Nations blue:
The UN emblem started as a publicity button for the 1945 San Francisco Conference where the UN Charter was drafted. It was designed by Donal McLaughlin (1907-2009), an architect by training and head of graphics and visual material in the OSS (US Office of Strategic Services, later the CIA).
The original insignia showed the globe, centred on the north pole, with North America on the central axis. In 1947, this orientation was changed by 90° so that the Greenwich meridian is at the centre, and all of South America is included.
The blue colour was meant to represent peace, the opposite of war which has traditionally been red. Blue was also the colour of the US Army, a relationship that started with the guerrilla nature of the War of Independence (1775-83) where blue uniforms offered more protective colouring than the opposing red British Army tunics.
PMS 279 is now the official UN blue colour, however Pantone system was not developed until 1963. At the time the flag was adopted, in 1947, the background colour was US Army gray-blue.
How curious and conflicted is the iconography of the UN, with its headquarters in New York and Geneva, its flag which at first privileged the United States and then Europe but now most significantly west Africa, its colour which came from a traditional US Army uniform colour but is now considered a universal cerulean blue, its globe wreathed in olive branches as Palestinian olive orchards are bulldozed to build a security fence ignoring dozens of UN Resolutions, the optimism of its original goals and the cynicism of the Security Council. In theory the leaders of every country can address the United Nations Assembly, but only if the United States gives them a visa to enter the US. It has, from the beginning, had a global reach based on the nation-state, which globalisation ignores.
However, its colour, especially when you consider its CMYK values, is extremely optimistic: the colour of sky on a sunny day, no black in it, so no shadows, no clouds, no pessimism.