Air Force blue colours are a variety of colours that are mostly various tones of the colour azure, the purest tones of which are identified as being the colour of the sky on a clear day. Some air force blue colours, notably the air force blue colour used by the United States Air Force and the colour used by the US Air Force Academy, may look like they are tones of blue instead of azure. However, they are actually dark tones of azure, not blue. These air force blue colours are used by these various air forces for colour identification.