Violet (color) in the context of "Purple"

In color theory, hue is one of the properties (called color appearance parameters) of a color, defined in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, orange, yellow, green, blue, violet," within certain theories of color vision.

Hue can typically be represented quantitatively by a single number, often corresponding to an angular position around a central or neutral point or axis on a color space coordinate diagram (such as a chromaticity diagram) or color wheel, or by its dominant wavelength or by that of its complementary color. The other color appearance parameters are colorfulness, saturation (also known as intensity or chroma), lightness, and brightness. Usually, colors with the same hue are distinguished with adjectives referring to their lightness or colorfulness - for example: "light blue", "pastel blue", "vivid blue", and "cobalt blue". Exceptions include brown, which is a dark orange.

Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–750 nanometers. It is a primary color in the RGB color model and a secondary color (made from magenta and yellow) in the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy.

Red pigment made from ochre was one of the first colors used in prehistoric art. The Ancient Egyptians and Mayans colored their faces red in ceremonies; Roman generals had their bodies colored red to celebrate victories. It was also an important color in China, where it was used to color early pottery and later the gates and walls of palaces. In the Renaissance, the brilliant red costumes for the nobility and wealthy were dyed with kermes and cochineal. The 19th century brought the introduction of the first synthetic red dyes, which replaced the traditional dyes. Red became a symbolic color of communism and socialism; Soviet Russia adopted a red flag following the Bolshevik Revolution in 1917. The Soviet red banner would subsequently be used throughout the entire history of the Soviet Union. China adopted its own red flag following the Chinese Communist Revolution. A red flag was also adopted by North Vietnam in 1954, and by all of Vietnam in 1975.

A lunar eclipse, also called a blood moon, is an astronomical event that occurs when the Moon orbits through Earth's shadow.‍‍ Lunar eclipses occur during eclipse season, when the Moon's orbital plane is approximately in line with Earth and the Sun. The type and length of a lunar eclipse depend on the Moon's proximity to the lunar node.‍‍ In contrast with illusive and short-lasting solar eclipses, lunar eclipses can be observed from anywhere on the night side of Earth and often last for an hour or longer. Lunar eclipses are safe to observe without eye protection.

Lunar eclipses are notable for causing the Moon to appear orange or red. This occurs when the Moon passes through the Earth's umbra, necessitating any sunlight that reaches the Moon to first pass through the Earth's atmosphere. The resulting Rayleigh scattering removes high-wavelength colors such as violet and blue from the incoming light before it reflects off the lunar surface and is observed on Earth.

Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος amethystos from α- a-, "not" and μεθύσκω (Ancient Greek) methysko / μεθώ metho (Modern Greek), "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. Ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxication.

Amethyst, a semiprecious stone, is often used in jewelry.

Blue is one of the three primary colours in the RGB (additive) colour model, as well as in the RYB colour model (traditional colour theory). It lies between violet and cyan on the spectrum of visible light. The term blue generally describes colours perceived by humans observing light with a dominant wavelength between approximately 450 and 495 nanometres. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called the Tyndall effect explains blue eyes. Distant objects appear more blue because of another optical effect called aerial perspective.

Blue has been an important colour in art and decoration since ancient times. The semi-precious stone lapis lazuli was used in ancient Egypt for jewellery and ornament and later, in the Renaissance, to make the pigment ultramarine, the most expensive of all pigments. In the eighth century Chinese artists used cobalt blue to colour fine blue and white porcelain. In the Middle Ages, European artists used it in the windows of cathedrals. Europeans wore clothing coloured with the vegetable dye woad until it was replaced by the finer indigo from America. In the 19th century, synthetic blue dyes and pigments gradually replaced organic dyes and mineral pigments. Dark blue became a common colour for military uniforms and later, in the late 20th century, for business suits. Because blue has commonly been associated with harmony, it was chosen as the colour of the flags of the United Nations and the European Union.

The Porvoo Communion is a communion of 15 predominantly northern European Anglican and Evangelical Lutheran churches, with some church bodies in the Iberian Peninsula of the same denomination. It was established in 1992 by a theological agreement entitled the Porvoo Common Statement which establishes full communion between and among these churches. The agreement was negotiated in the town of Järvenpää in Finland, but the communion's name comes from the nearby city of Porvoo, where a joint Eucharist (or Holy Communion) was celebrated in Porvoo Cathedral after the formal signing in Järvenpää. The Porvoo Communion claims to represent 45 million members among the member churches, approximately 50% of Europe's Protestants.