Of clothing: dark, sombre; spec. designating the dark formal attire worn for examinations and other occasions at certain universities (cf. sense…

Of a garment, now typically worn at work: having a blue collar.

transferred. attributive (19th cent.) Applied to articles of apparel of a ‘loud’ or ‘flashy’ style, or combining two strongly contrasted colours.

Of a dark, dusky, or dull colour; sombre, subdued, gloomy.

Designating a type of tweed or a garment made of this; (also) designating a muted shade of a colour characteristic of this tweed, or something…

Of a pinkish beige colour.