trueblue

Noun

true blue (countable and uncountable, plural true blues)

1. (countable) A faithful partisan or supporter of a cause, person, political party, etc.
   • A mild Liberalism prevailed, a Liberalism that would be regarded as hide-bound Toryism now, but was daring enough in those days. One man who had been to work in Northampton proclaimed himself a Radical; but he was cancelled out by the landlord, who called himself a ‘true blue’.1939, Flora Thompson, “At the ‘Wagon and Horses’”, in Lark Rise to Candleford: A Trilogy, London: Penguin Books, published 1973, →ISBN, pages 65–66
2. (historical, uncountable) A blue dye from Coventry, England, famous for not washing out.
3. (color models and color spaces) A precisely defined pure blue, as for example web color #0000FF = RGB(0,0,255).

See all 11 meanings of true blue