Traditionally seen as the colour of constancy, as well as the colour of sorrow and anguish, and of plagues and hurtful things. It is also associated with the male sex (as pink is with the female sex).
Politically, the colour was associated with the Scottish Presbyterian or Whig party in the 17th century, and later with the Tory, and then Conservative, party.
At Oxford and Cambridge Universities, a blue is a person who has represented Cambridge (a Cambridge Blue) or Oxford (an Oxford Blue) in a particular sport.
The informal sense of blue to mean ‘obscene, indecent, profane’ developed in the mid 19th century.
blue are the hills that are far away a view seen from a distance has an added attraction (a similar idea is expressed by distance of Chancery). A northern saying, recorded from the late 19th century (green is sometimes found instead of blue). The thought is echoed in Housman's line from A Shropshire Lad (1896) ‘What are those blue remembered hills’.
blue blood that which is traditionally said to flow in the veins of old and aristocratic families; the term is a translation of Spanish sangre azul, attributed to Castilian families who claimed to have no admixture of Moorish, Jewish, or other foreign blood. The expression may have originated in the blueness of the veins of people of fair complexion as compared with those of dark skin.
blue boar the heraldic cognizance of Richard Duke of York (1411–60), father of Edward IV and Richard III.
Blue Bonnets Scots soldiery (also called Blue Caps), from the broad round horizontally flattened bonnet or cap of blue woollen material, formerly widely worn in Scotland.
blue book in the UK, a report bound in a blue cover and issued by Parliament or the Privy Council; in the US, an official book listing government officials.
blue-chip denoting companies or their shares considered to be a reliable investment, though less secure than gilt-edged stock. The term comes (in the early 20th century) from the US; from the blue chip used in gambling games, which usually has a high value.
Blue Coat a student at a charity school with a blue uniform which represents the blue coat traditionally worn by an almoner; the name is particularly associated with Christ's Hospital School, whose uniform is a long dark blue gown fastened at the waist with a belt, and bright yellow stockings.
blue-collar worker a manual worker, particularly in industry; the term is recorded (originally in the US) from the 1950s.
blue-eyed boy a person highly regarded by someone and treated with special favour; the term is first recorded in a novel by P. G. Wodehouse in 1924.
blue flag a European award for beaches based on cleanliness and safety.
Blue Hen's Chickens inhabitants of the state of Delaware. The term is said to have come from a company in the American War of Independence, led by a Captain Caldwell of Delaware, who were known in Carolina firstly as ‘Caldwell's gamecocks’, and then ‘the blue hen's chickens’ and the ‘blue chickens’. From this, the name ‘Blue Hen’ was given to the state.