Rainbow Codes

The Rainbow Codes were a series of code names used to disguise the nature of various British military research projects. They were mainly used from after the Second World War until 1958, when they were replaced by an alphanumeric code system.

The Ministry of Supply (MoS) initiated the idea because, during World War II, the British realised that although the code-names of some German secret projects could be cryptic, they often provided useful clues as to their nature. For example, basic characteristics of a new German radio navigation device known as Wotan (which used a single radio beam) were inferred by the British before it entered service with the Luftwaffe. This was because the system was named after the one-eyed god of the same name, which offered British scientists a useful hint. The intention of rainbow codes was to clearly and uniquely identify British projects, whilst not providing any hints or clues regarding their characteristics.

Each rainbow code name was constructed from a randomly selected colour, plus an (often appropriate) noun taken from a list, for example:

While most colour and noun combinations were meaningless, some were real names, although quite unrelated to the project they designated. For example, "Black Maria" is also a name for a police van and the "Red Duster" is a name for the Red Ensign, the flag flown by British merchant ships.

The names were mostly dropped with the end of the Ministry in 1959. Its functions were transferred to the War Office, the Air Ministry that handled military aviation, and the newly created Ministry of Aviation in charge of civil aviation. After the reorganization, projects were mostly named with randomly selected codes comprising two letters and three digits, e.g. BL755, WE.177. However, rainbow codes continue to be used with some modern systems; current examples include the Blue Vixen radar and the Orange Reaper Electronic Support Measures system.

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