E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
In England, parliamentary reports and official publications presented by the Crown to both Houses of Parliament. Each volume is in folio, and is covered with a blue wrapper.
Short Acts of Parliament, etc., even without a wrapper, come under the same designation.
In America, the Blue Books (like our Red Books) contain lists of those persons who hold government appointments. The official colour of Spain is red, of Italy green, of France yellow, of Germany and Portugal white.