green

green, in physics, light in the wavelength range of 495–570 nanometres, which is in the middle of the visible spectrum. In art, green is a colour on the conventional colour wheel, located between yellow and blue and opposite red, its complementary colour.

Green is a basic colour term added to languages before or after yellow, following black, white, and red. The word green derives from Proto-Germanic grōni and Old English grene. One of the first written records of the term is from the Caedmon Manuscript (c. 1000 ce): “Adam stop / On grene græs, gaste geweorthad” (“Adam stepped / On green grass, soul made worthy”).

Pigments for green come from malachite, cobalt oxide, zinc oxide, copper acetate, and artificial chemical compounds. In the 19th century, green pigment made with copper arsenite was known for its toxicity, and some supporters of Napoleon claimed that the fumes from the green wallpaper at Longwood House on St. Helena island, his place of exile, contributed to his death.

In addition to the colour wheel, various other colour systems have been used to classify green. 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 “Duck Green” is compared to the “Neck of Mallard,” the “Upper Disk of Yew Leaves,” and “Ceylanite.” In the Munsell colour system—adopted in the early 20th century to standardize colour, usually for industry—one of the many variations of green is identified as 2.5G 5/24.