- blue: of the color intermediate between green and violet; having a color similar to that of a clear unclouded sky; "October's bright blue weather"- Helen Hunt Jackson; "a blue flame"; "blue haze of tobacco smoke"
- Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. ...
- Having a tint or hue similar to or comprised of the colour blue; Somewhat depressed; sad
- (young adult novel) 1999