Generally associated with purple (Exodus 25:4; 26:1, 31, 36, etc.). It is supposed to have been obtained from a shellfish of the Mediterranean, the Helix ianthina of Linnaeus. The robe of the high priest's ephod was to be all of this colour (Exodus 28:31), also the loops of the curtains (26:4) and the ribbon of the breastplate (28:28). Blue cloths were also made for various sacred purposes (Numbers 4:6, 7, 9, 11, 12). (see COLOUR.)

Noah Webster's New International Dictionary of the English Language

1. (superl.) Having the color of the clear sky, or a hue resembling it, whether lighter or darker; as, the deep, blue sea; as blue as a sapphire; blue violets.

2. (superl.) Pale, without redness or glare, -- said of a flame; hence, of the color of burning brimstone, betokening the presence of ghosts or devils; as, the candle burns blue; the air was blue with oaths.

3. (superl.) Low in spirits; melancholy; as, to feel blue.

4. (superl.) Suited to produce low spirits; gloomy in prospect; as, thongs looked blue.

5. (superl.) Severe or over strict in morals; gloom; as, blue and sour religionists; suiting one who is over strict in morals; inculcating an impracticable, severe, or gloomy mortality; as, blue laws.

6. (superl.) Literary; -- applied to women; -- an abbreviation of bluestocking.

7. (n.) One of the seven colors into which the rays of light divide themselves, when refracted through a glass prism; the color of the clear sky, or a color resembling that, whether lighter or darker; a pigment having such color. Sometimes, poetically, the sky.

8. (n.) A pedantic woman; a bluestocking.

9. (pl.) Low spirits; a fit of despondency; melancholy.

10. (v. t.) To make blue; to dye of a blue color; to make blue by heating, as metals, etc.