During post-classical and early modern Europe, green was the color commonly associated with wealth, merchants, bankers, and the gentry, while red was reserved for the nobility.

[2] In surveys made in American, European, and Islamic countries, green is the color most commonly associated with nature, life, health, youth, spring, hope, and envy.

Thus, the languages mentioned above (Germanic, Romance, Slavic, Greek) have old terms for "green" which are derived from words for fresh, sprouting vegetation.

However, comparative linguistics makes clear that these terms were coined independently, over the past few millennia, and there is no identifiable single Proto-Indo-European or word for "green".

In optics, the perception of green is evoked by light having a spectrum dominated by energy with a wavelength of roughly 495–570 nm.

A green light source typically has a spectral power distribution dominated by energy with a wavelength of roughly 487–570 nm.

Green laser pointers outputting at 532 nm (563.5 THz) are relatively inexpensive compared to other wavelengths of the same power, and are very popular due to their good beam quality and very high apparent brightness.

[29] Verdigris is made by placing a plate or blade of copper, brass or bronze, slightly warmed, into a vat of fermenting wine, leaving it there for several weeks, and then scraping off and drying the green powder that forms on the metal.

Chlorophyll, the E numbers E140 and E141, is the most common green chemical found in nature, and only allowed in certain medicines and cosmetic materials.

[38] Chlorophyll absorbs green light poorly because it first arose in organisms living in oceans where purple halobacteria were already exploiting photosynthesis.

[17] Most fish, reptiles, amphibians, and birds appear green because of a reflection of blue light coming through an over-layer of yellow pigment.

Substances that may impart a greenish hue to one's skin include biliverdin, the green pigment in bile, and ceruloplasmin, a protein that carries copper ions in chelation.

There is no green pigment in green eyes; like the color of blue eyes, it is an optical illusion; its appearance is caused by the combination of an amber or light brown pigmentation of the stroma, given by a low or moderate concentration of melanin, with the blue tone imparted by the Rayleigh scattering of the reflected light.

Following birth, cells called melanocytes start to discharge melanin, the earthy colored shade, in the child's irises.

Ceramics from ancient Mesopotamia show people wearing vivid green costumes, but it is not known how the colors were produced.

[47] In Ancient Egypt, green was the symbol of regeneration and rebirth, and of the crops made possible by the annual flooding of the Nile.

Tombs also often contained small green amulets in the shape of scarab beetles made of malachite, which would protect and give vigor to the deceased.

Red could only be worn by the nobility, brown and gray by peasants, and green by merchants, bankers and the gentry and their families.

[53] The pigments available to painters were more varied; monks in monasteries used verdigris, made by soaking copper in fermenting wine, to color medieval manuscripts.

[55] The German poet and philosopher Goethe declared that green was the most restful color, suitable for decorating bedrooms.

Painters such as John Constable and Jean-Baptiste-Camille Corot depicted the lush green of rural landscapes and forests.

Describing his painting, The Night Cafe, to his brother Theo in 1888, Van Gogh wrote: "I sought to express with red and green the terrible human passions.

[58] The first traffic light, using green and red gas lamps, was erected in 1868 in front of the Houses of Parliament in London.

[69] Experimental studies also show this calming effect in a statistical significant decrease of negative emotions[70] and increase of creative performance.

Actor Bela Lugosi wore green-hued makeup for the role of Dracula in the 1927–1928 Broadway stage production.

From the Middle Ages to the 19th century it was often worn by bankers, merchants country gentlemen and others who were wealthy but not members of the nobility.

Several African countries thus use the color on their flags, including Nigeria, South Africa, Ghana, Senegal, Mali, Ethiopia, Togo, Guinea, Benin, and Zimbabwe.

In 532 AD rioting between the factions began after one race, which led to the massacre of green supporters and the destruction of much of the center of Constantinople.

Green parties in Europe have programs based on ecology, grassroots democracy, nonviolence, and social justice.

[110] Roman Catholic and more traditional Protestant clergy wear green vestments at liturgical celebrations during Ordinary Time.