Blue Book

The term Blue Book refers to a category of official government documents, named for the blue paper covers historically used to bind reports laid before Parliament in the United Kingdom. The format dates to the 17th century and became standard in the 19th century for command papers, royal commission reports, diplomatic correspondence, and statistical returns presented to the House of Commons.

In British usage, Blue Books have included some of the most consequential state documents of their era. Diplomatic Blue Books were used to publish correspondence between the Foreign Office and overseas missions, allowing Parliament and the public to scrutinize foreign policy. Colonial Blue Books, compiled annually in each British colony, recorded population, revenue, expenditure, trade, and administrative statistics, and are now key primary sources for historians of empire.

The term has been adopted with varying meanings elsewhere:

• In the United States, "Blue Book" can refer to the Official Congressional Directory and to various agency manuals; the Department of State has historically used the term for diplomatic lists.
• In Canada and Australia, the Blue Book or "Blues" often denotes departmental estimates and Hansard-related publications.
• In diplomacy, "Blue Book" is sometimes used informally for the diplomatic list of accredited foreign envoys maintained by a host country's foreign ministry.
• In intelligence history, Project Blue Book (1952–1969) was the US Air Force's study of UFO reports—an unrelated but well-known use of the name.

Blue Books are distinguished from White Papers (government policy statements) and Green Papers (consultative documents), though all three are forms of command papers in the Westminster tradition. For researchers, Blue Books are valuable because they typically contain primary documentation—treaty texts, dispatches, statistical tables—rather than interpretive commentary, making them useful for citation in historical and policy research.