White in the context of Red

The contrast of white and black (light and darkness, day and night) has a long tradition of metaphorical usage, traceable to the Ancient Near East, and explicitly in the Pythagorean Table of Opposites.In Western culture as well as in Confucianism, the contrast symbolizes the moral dichotomy of good and evil.

An optical prism is a transparent optical element with flat, polished surfaces that are designed to refract light. At least one surface must be angled—elements with two parallel surfaces are not prisms. The most familiar type of optical prism is the triangular prism, which has a triangular base and rectangular sides. Not all optical prisms are geometric prisms, and not all geometric prisms would count as an optical prism. Prisms can be made from any material that is transparent to the wavelengths for which they are designed. Typical materials include glass, acrylic and fluorite.

A dispersive prism can be used to break white light up into its constituent spectral colors (the colors of the rainbow) to form a spectrum as described in the following section. Other types of prisms noted below can be used to reflect light, or to split light into components with different polarizations.

Complementary colors are pairs of colors which, when combined or mixed, cancel each other out (lose chroma) by producing a grayscale color like white or black. When placed next to each other, they create the strongest contrast for those two colors. Complementary colors may also be called "opposite colors".

Which pairs of colors are considered complementary depends on the color model that one uses:

Cyan (/ˈsaɪ.ən, -æn/) is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue.

In the subtractive color system, or CMYK color model, which can be overlaid to produce all colors in paint and color printing, cyan is one of the primary colors, along with magenta and yellow. In the additive color system, or RGB color model, used to create all the colors on a computer or television display, cyan is made by mixing equal amounts of green and blue light. Cyan is the complement of red; it can be made by the removal of red from white. Mixing red light and cyan light at the right intensity will make white light. It is commonly seen on a bright, sunny day in the sky.

Black is a color that results from the absence or complete absorption of visible light. It is an achromatic color, without chroma, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white have often been used to describe opposites such as good and evil, the Dark Ages versus the Age of Enlightenment, and night versus day. Since the Middle Ages, black has been the symbolic color of solemnity and authority, and for this reason it is still commonly worn by judges and magistrates.

Black was one of the first colors used by artists in Neolithic cave paintings. It was used in ancient Egypt and Greece as the color of the underworld. In the Roman Empire, it became the color of mourning, and over the centuries it was frequently associated with death, evil, witches, and magic. In the 14th century, it was worn by royalty, clergy, judges, and government officials in much of Europe. It became the color worn by English romantic poets, businessmen and statesmen in the 19th century, and a high fashion color in the 20th century. According to surveys in Europe and North America, it is the color most commonly associated with mourning, the end, secrets, magic, force, violence, fear, evil, and elegance.

The Natural Colour System (NCS) is a proprietary perceptual color model. It is based on the color opponency hypothesis of color vision, first proposed by German physiologist Ewald Hering. The current version of the NCS was developed by the Swedish Colour Centre Foundation, from 1964 onwards. The research team consisted of Anders Hård, Lars Sivik and Gunnar Tonnquist, who in 1997 received the AIC Judd award for their work. The system is based entirely on the phenomenology of human perception as opposed to color mixing. It is illustrated by a color atlas, marketed by NCS Colour AB in Stockholm.

Black-and-white (B&W or B/W) images combine black and white to produce a range of achromatic brightnesses of grey. It is also known as greyscale in technical settings.

Variations of gray or grey include achromatic grayscale shades, which lie exactly between white and black, and nearby colors with low colorfulness. A selection of a number of these various colors is shown below.

In digital photography, computer-generated imagery, and colorimetry, a grayscale (American English) or greyscale (Commonwealth English) image is one in which the value of each pixel holds no color information and only expresses a shade of gray. Pixel values are typically stored in the range 0 to 255 (black to white).

Grayscale images, are black-and-white or gray monochrome, and composed exclusively of shades of gray. The contrast ranges from black at the weakest intensity to white at the strongest. Grayscale images are distinct from one-bit bi-tonal black-and-white images, which, in the context of computer imaging, are images with only two colors: black and white (also called bilevel or binary images). Grayscale images have many shades of gray in between.

In color theory, a tint is a mixture of a color with white, which increases lightness, while a shade is a mixture with black, which increases darkness. A tone is produced either by mixing a color with gray, or by both tinting and shading. Mixing a color with any neutral color (black, gray, and white) reduces the chroma, or colorfulness, while the perceived hue can be affected slightly (see Abney effect and Bezold-Brücke shift).

In the graphic arts, especially printmaking and drawing, "tone" has a different meaning, referring to areas of continuous color, produced by various means, as opposed to the linear marks made by an engraved or drawn line.

The opponent process is a hypothesis of color vision that states that the human visual system interprets information about color by processing signals from the three types of photoreceptor cells in an antagonistic manner. The three types of cones are called L, M, and S. The names stand for "Long wavelength sensitive,” "middle wavelength sensitive," and "short wavelength sensitive." The opponent-process theory implicates three opponent channels: L versus M, S versus (L+M), and a luminance channel (+ versus -). These cone-opponent mechanisms were at one time thought to be the neural substrate for a psychological theory called Hering's Opponent Colors Theory, which calls for three psychologically important opponent color processes: red versus green, blue versus yellow, and black versus white (luminance). The Opponent Colors Theory is named for the German physiologist Ewald Hering who proposed the idea in the late 19th century. However, it has been argued that Hering’s Opponent Colors Theory lacks adequate phenomenological and empirical support, and may not be a necessary feature of normal human color experience. Correspondingly, considerable physiological and behavioral evidence proves that the physiological cone opponent mechanisms do not constitute the neurobiological basis for Hering's Opponent Colors Theory.

The national flag of France (French: Drapeau national de la France) is a tricolour featuring three vertical bands coloured blue (hoist side), white, and red. The design was adopted during the French Revolution and has remained the national flag since then, with only minor variations in shade and proportion. While not the first tricolour, it became one of the most influential flags in history. The tricolour scheme was later adopted by many other nations in Europe and elsewhere, and, according to the Encyclopædia Britannica, has historically stood "in symbolic opposition to the autocratic and clericalist royal standards of the past".

Before the tricolour was adopted the royal government used many flags, the best known being a blue shield and gold fleurs-de-lis (the Royal Arms of France) on a white background, or state flag. Early in the French Revolution, the Paris militia, which played a prominent role in the storming of the Bastille, wore a cockade of blue and red, the city's traditional colours. According to French general Gilbert du Motier, Marquis de Lafayette, white was the "ancient French colour" and was added to the militia cockade to form a tricolour, or national, cockade of France.

The pan-Arab colors are black, white, green and red. Individually, each of the four pan-Arab colors were intended to represent a certain aspect of the Arab people and their history.

Russian churches often have various recurrent elements in their architecture. The onion dome is for example a recurrent and important element in the architecture of Russian churches. Often Russian churches have also multi-colored filigree ornamental elements. Furthermore the colour white plays an important role in the style of Russian churches. In the past, Russian churches were made out of wood. Many Russian Orthodox churches are distinguished by their verticality, bright colors and multiple domes, which provide a striking contrast with the flat Russian landscape, often covered in snow. The first churches in Kievan Rus', such as the 13-domed wooden Cathedral of St. Sophia, Novgorod, differed in this regard from their mainly single-dome Byzantine predecessors. The number of domes was important symbolically. One dome symbolized the single God; three represented the Trinity, and five represented Christ and his four evangelists. At first the baptistery, narthex, and choir gallery above the narthex were a common feature of Rus' churches, but gradually they disappeared. After a century of Byzantine imitations, the Russian masons began to emphasise the verticality in church design.

The late 12th century saw the development of so-called tower churches in Polotsk and Smolensk; this design later spread to other areas such as Kiev and Chernihiv. A visual transition between the main cube of the church and the elongated cylinder below the dome was provided by one or several rows of curved corbel arches, known as kokoshniki. They could be spade-shaped, semicircular, or pointed. In later Muscovite churches, the massed banks of kokoshniki evolved into a distinctive pyramidal shape. The reign of Ivan the Terrible was marked by the introduction of so-called tented roofs. The churches such as St. Basil's Cathedral were an agglomeration of chapels capped by the steeply pitched conical roofs of fanciful designs.