The colour of the clear sky or the deep sea; the colour midway between green and violet in the visible spectrum and one of the primary additive colours. • Anything coloured blue, especially to distinguish it from similar objects differing only in colour. • A blue dye or pigment. • Blue clothing. • A blue uniform. See blues. • A member of a sports team that wears blue colours; (in the plural) a nickname for the team as a whole. See also blues. • An umpire, in reference to the typical dark-blue colour of the umpire's uniform. Sometimes perceived by umpires as derogatory when used by players or coaches while disputing a call. • Sporting colours awarded by a university or other institution for sporting achievement, such as representing one's university, especially and originally at Oxford and Cambridge Universities in England. See also full blue, half blue. • A person who has received such sporting colours. • A member of law enforcement. • A bluestocking. • The sky, literally or figuratively. • The ocean; deep waters. • The far distance; a remote or distant place. • A dog or cat with a slaty gray coat. • One of the colour balls used in snooker, with a value of five points. • Any of the butterflies of the subfamily Polyommatinae in the family Lycaenidae, most of which have blue on their wings. • A bluefish. • An argument or brawl. • A liquid with an intense blue colour, added to a laundry wash to prevent yellowing of white clothes. • Any of several processes to protect metal against rust. • A type of firecracker. • One of the three colour charges for quarks. • A member or supporter of the Conservative Party. • A blue cheese. • Risqué or pornographic material.