Rainbow Code

The Rainbow Codes were a series of code names used to disguise the nature of various British military research projects. They were mainly used by the Ministry of Supply from the end of the Second World War until 1958, when the ministry was broken up and its functions distributed among the forces. The codes were replaced by an alphanumeric code system.
History.
During WWII, British intelligence was able to glean details of new German technologies simply by considering their code names. For instance, when they began hearing of a new system known as "Wotan", Reginald Victor Jones asked around and found that Wotan was a one-eyed god. Based on this, he guessed it was a radio navigation system using a single radio beam. This proved correct, and the Royal Air Force was able to quickly render it useless through jamming.
Looking to avoid making this sort of mistake, Ministry of Supply (MoS) initiated a system that would be entirely random and deliberately unrelated to the program in any way, while still being easy to remember. 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. Some code names were not assigned through the official system, but created to sound like it. An example is the Blue Yeoman radar, an unofficial name created by combining the names of two other projects, Blue Riband and Orange Yeoman.
The names were mostly dropped with the end of the Ministry in 1959. Its functions were split between the War Office, the Air Ministry, and the newly created Ministry of Aviation for civil aviation. After the reorganization, projects were mostly named with randomly selected codes comprising two letters and three digits, e.g. BL755, WE.177. Rainbow codes, or at least names that look like them without being official, have occasionally been used for some modern systems; current examples include the Orange Reaper Electronic Support Measures system and the Blue Vixen radar—the latter most likely so named because it was a replacement for the Blue Fox radar.
Non-Rainbow codes.
Several British military related terms have a similar "colour" format to Rainbow Codes, but are not since they do not refer to classified research projects, and some names have been used unofficially. These include: