Definition of "blue" []

• The hue of that portion of the visible spectrum lying between green and indigo, evoked in the human observer by radiant energy with wavelengths of approximately 420 to 490 nanometers; any of a group of colors that may vary in lightness and saturation, whose hue is that of a clear daytime sky; one of the additive or light primaries; one of the psychological primary hues. (noun)
• A pigment or dye imparting this hue. (noun)
• Bluing. (noun)
• An object having this hue. (noun)
• Dress or clothing of this hue: The ushers wore blue. (noun)
• Any of a group of colours, such as that of a clear unclouded sky, that have wavelengths in the range 490–445 nanometres. Blue is the complementary colour of yellow and with red and green forms a set of primary colours (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• A dye or pigment of any of these colours (noun)
• Blue cloth or clothing (noun)
• A sportsperson who represents or has represented Oxford or Cambridge University and has the right to wear the university colour (dark blue for Oxford, light blue for Cambridge) (noun)
• The honour of so representing one's university (noun)
• Any of numerous small blue-winged butterflies of the genera Lampides, Polyommatus, etc: family Lycaenidae (noun)
• A policeman (noun)
• A blue ring on a target, between the red and the black, scoring five points (noun)
• A blue ball in snooker, etc (noun)
• An argument or fight (noun)
• A court summons, esp for a traffic offence (noun)
• A mistake; error (noun)
• Of the colour blue (adjective)
• (of the flesh) having a purple tinge, as from cold or contusion (adjective)
• Depressed, moody, or unhappy (adjective)
• Dismal or depressing (adjective)
• Indecent, titillating, or pornographic (adjective)
• Bluish in colour or having parts or marks that are bluish (adjective)
• Aristocratic; noble; patrician (adjective)
• Relating to, supporting, or representing the Democratic Party (adjective)
• To make, dye, or become blue (verb)
• To treat (laundry) with blueing (verb)
• To spend extravagantly or wastefully; squander (verb)

www.Collinsdictionary.com (c) HarperCollins Publishers Ltd 2016

• "Light blue is more specific than ˜blue™ which is more specific than ˜colored.™"
• "The blue stains, the lines for corrections, etc., are erased with the the potassic oxalate (_blue salving, _ as it is termed) whose formula has been given."
• "It is scarcely more previous than the underlying limestones, and why a solution that could penetrate and leach ores from it should be stopped at the upper surface of the blue limestone is not obvious; nor why the plane of junction between the porphyry and the _blue limestone_ should be the special place of deposit of the ore."