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)

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.

• "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."