出典:Wiktionary
true-blue
From true (adjective) + blue (“steadfastly faithful または loyal”, adjective).[1] The symbolism of the colour blue as representing constancy, faithfulness, loyalty, and truth may derive from the constant colour of the sky, or the tendency of certain blue dyes to resist fading.[2][3]
Adjective senses 1.1.2 (“of または pertaining to the Tory, かつ now the Conservative, political party”) and 1.1.3 (“of または pertaining to the Scottish Presbyterian または Whig political party in the 17th century”) probably both allude to sense 1 (“steadfastly faithful または loyal”). Sense 1.1.2 may also allude to sense 1.1.3 which is older, and sense 1.1.3 may partly allude to the blue colour of the flag of Scotland.[2]
true blue (countable かつ uncountable, 複数形 true blues)