Eton Blue or ‘Shelduck Blue’ is a shade of green used by Eton College athletes since the early 19th century. It is also used by Geelong Grammar School and is similar to the Cambridge University color (Cambridge Blue). Chelsea FC have worn Eton Blue since their formation in 1905, as the Earl of Cadogan, the club’s president and holder of the title of Viscount Chelsea, was a former Etonian. They switched to their darker royal blue in 1907.