blue, inphysics,light in thewavelength range of 450–495 nanometres in the visiblespectrum. Afterviolet, blue is the spectral region with the shortest wavelengths discernible to thehuman eye. Inart, blue is a colour on theconventionalcolour wheel, located betweengreen andviolet and oppositeorange, its ccomplementary colour.

Blue is a basic colour term added to languages afterblack,white,red,yellow, andgreen. The termblue derives from Proto-Germanicblæwaz and Old Frenchblo orbleu. One of the first written records of the term is from theSouth English Legendary, a collection of saints’ lives (c. 1300): “This on schal beo fair blu cloth, / This othur grene” (“This one shall be fair blue cloth, / This other green”).

Pigments for blue have come fromazurite,ultramarine, smalt,indigo, a double oxide ofcobalt and aluminum, and artificial chemicalcompounds. Indigo was used as adye to colour cloth for trousers, which became known asblue jeans.

Britannica Quiz

The Origins of Colors, Pigments, and Dyes

In addition to the colour wheel, various other colour systems have been used to classify blue. Before the invention of colour photography,Werner’s Nomenclature of Colour (1814) was frequently used by scientists attempting to accurately describe colours observed in nature. In that book the so-called tint “Prussian Blue” is compared to the “Beauty Spot on Wing of Mallard Drake,” the “Stamina of Bluish Purple Anemone,” and “Blue Copper Ore.” In theMunsell colour system—adopted in the 20th century to standardize colour, usually for industry—one of the many variations of blue is identified as 5PB 4/14.