Colour in the context of Colorfulness

A colourant/colour additive (British spelling) or colorant/color additive (American spelling) is a substance that is added or applied in order to change the colour of a material or surface. Colourants can be used for many purposes including printing, painting, and for colouring many types of materials such as foods and plastics. Colourants work by absorbing varying amounts of light at different wavelengths (or frequencies) of its spectrum, transmitting (if translucent) or reflecting the remaining light in straight lines or scattered.

Most colourants can be classified as dyes or pigments, or containing some combination of these. Typical dyes are formulated as solutions, while pigments are made up of solid particles suspended and are generally suspended in a vehicle (e.g., linseed oil). The colour a colourant imparts to a substance is mediated by other ingredients it is mixed with such as binders and fillers are added, for example in paints and inks. In addition, some colourants impart colour through reactions with other substances.

Orange is the colour between yellow and red on the spectrum of visible light. The human eyes perceive orange when observing light with a dominant wavelength between roughly 585 and 620 nanometres. In traditional colour theory, it is a secondary colour of pigments, produced by mixing yellow and red. In the RGB colour model, it is a tertiary colour. It is named after the fruit of the same name.

The orange colour of many fruits and vegetables, such as carrots, pumpkins, sweet potatoes, and oranges, comes from carotenes, a type of photosynthetic pigment. These pigments convert the light energy that the plants absorb from the Sun into chemical energy for the plants' growth. Similarly, the hues of autumn leaves are from the same pigment after chlorophyll is removed.

Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear gradually to change colour as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light in microstructures or thin films. Examples of iridescence include soap bubbles, feathers, butterfly wings and seashell nacre, and minerals such as opal. Pearlescence is a related effect where some or most of the reflected light is white. The term pearlescent is used to describe certain paint finishes, usually in the automotive industry, which actually produce iridescent effects.

An Amici prism, named for the astronomer Giovanni Battista Amici, is a type of compound dispersive prism used in spectrometers. The Amici prism consists of two triangular prisms in contact, with the first typically being made from a medium-dispersion crown glass, and the second from a higher-dispersion flint glass. Light entering the first prism is refracted at the first air–glass interface, refracted again at the interface between the two prisms, and then exits the second prism at near-normal incidence. The prism angles and materials are chosen such that one wavelength (colour) of light, the centre wavelength, exits the prism parallel to (but offset from) the entrance beam. The prism assembly is thus a direct-vision prism and is commonly used as such in hand-held spectroscopes. Other wavelengths are deflected at angles depending on the glass dispersion of the materials. Looking at a light source through the prism thus shows the optical spectrum of the source.

By 1860, Amici realized that one can join this type of prism back-to-back with a reflected copy of itself, producing a three-prism arrangement known as a double Amici prism. This doubling of the original prism increases the angular dispersion of the assembly and also has the useful property that the centre wavelength is refracted back into the direct line of the entrance beam. The exiting ray of the center wavelength is thus not only undeviated from the incident ray, but also experiences no translation (i.e. transverse displacement or offset) away from the incident ray's path.

Twinkling, also called scintillation, is a generic term for variations in apparent brightness, colour, or position of a distant luminous object viewed through a medium. If the object lies outside the Earth's atmosphere, as in the case of stars and planets, the phenomenon is termed astronomical scintillation; for objects within the atmosphere, the phenomenon is termed terrestrial scintillation. As one of the three principal factors governing astronomical seeing (the others being light pollution and cloud cover), atmospheric scintillation is defined as variations in illuminance only.

In simple terms, twinkling of stars is caused by the passing of light through different layers of a turbulent atmosphere. Most scintillation effects are caused by anomalous atmospheric refraction caused by small-scale fluctuations in air density usually related to temperature gradients. Scintillation effects are always much more pronounced near the horizon than near the zenith (directly overhead), since light rays near the horizon must have longer paths through the atmosphere before reaching the observer. Atmospheric twinkling is measured quantitatively using a scintillometer.

o-Xylene (ortho-xylene) is an aromatic hydrocarbon with the formula C₆H₄(CH₃)₂, with two methyl substituents bonded to adjacent carbon atoms of a benzene ring (the ortho configuration). It is a constitutional isomer of m-xylene and p-xylene, the mixture being called xylene or xylenes. o-Xylene is a colourless slightly oily flammable liquid.

Cream is the colour of the cream produced by cattle grazing on natural pasture with plants rich in yellow carotenoid pigments, some of which are incorporated into the fresh milk (specifically, the butterfat). This gives a yellow tone to otherwise-white milk at higher fat concentrations. Cream is the pastel colour of yellow, much as pink is to red. By mixing yellow and white, cream can be produced.

The first recorded use of cream as a colour name in English was in 1590.

Pheasants (/ˈfɛzənts/ FEH-zənts) are birds of several genera within the family Phasianidae in the order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera's native range is restricted to Eurasia. The classification "pheasant" is paraphyletic, as birds referred to as pheasants are included within both the subfamilies Phasianinae and Pavoninae, and in many cases are more closely related to smaller phasianids, grouse, and turkey (formerly classified in Perdicinae, Tetraoninae, and Meleagridinae) than to other pheasants.

Pheasants are characterised by strong sexual dimorphism, males being highly decorated with bright colours and adornments such as wattles. Males are usually larger than females and have longer tails. Males play no part in rearing the young.

Colour fastness is a term—used in the dyeing of textile materials—that characterizes a material's colour's resistance to fading or running. Colour fastness is the property of dyes and it is directly proportional to the binding force between photochromic dye and the fibre. The colour fastness may also be affected by processing techniques and choice of chemicals and auxiliaries.

The term is usually used in the context of clothes. In general, clothing should be tested for colour fastness before using bleach or other cleaning products. It can also apply to upholstery fabrics.

A mottle is a pattern of irregular marks, spots, streaks, blotches or patches of different shades or colours. The term commonly describes the surface of plants or the skin of animals. In plants, mottling usually consists of yellowish spots on plants, and is usually a sign of disease or malnutrition. Many plant viruses cause mottling, including Tobacco vein mottling virus and Bean pod mottle virus.

"Mottling" is sometimes used to describe uneven, discolored patches on the skin of humans as a result of cutaneous ischemia (lowered blood-flow to the surfaces of the skin) or Herpes zoster infections. The medical term for mottled skin is dyschromia. Although not always the case, mottling can occur in a dying patient and commonly indicates that the end of life is near. Mottling usually occurs in the extremities (lower first) and progresses up as cardiac function declines and circulation throughout the body is poor. In animals, mottling may be a sign of disease, but may also be a hereditary trait, as seen with the champagne and leopard complex genes in horses.

In heraldry, the background of the shield is called the field. The field is usually composed of one or more tinctures (colours or metals) or furs. The field may be divided or may consist of a variegated pattern.

In rare modern cases, the field or a subdivision thereof is not a tincture but is shown as a scene from a landscape, or, in the case of the 329th Fighter Group of the United States Air Force, blazoned as the sky proper. Landscape fields are regarded by many heralds as unheraldic and debased, as they defy the heraldic ideal of simple, boldly-coloured images, and they cannot be consistently drawn from blazon.

Fawn is a light yellowish tan colour. It is usually used in reference to clothing, soft furnishings and bedding, as well as to a dog's coat colour. It occurs in varying shades, ranging between pale tan to pale fawn to dark deer-red.The first recorded use of fawn as a colour name in English was in 1789.

In chemistry, solvatochromism is the phenomenon observed when the colour of a solution is different when the solute is dissolved in different solvents.

The solvatochromic effect is the way the spectrum of a substance (the solute) varies when the substance is dissolved in a variety of solvents. In this context, the dielectric constant and hydrogen bonding capacity are the most important properties of the solvent. With various solvents there is a different effect on the electronic ground state and excited state of the solute, so that the size of energy gap between them changes as the solvent changes. This is reflected in the absorption or emission spectrum of the solute as differences in the position, intensity, and shape of the spectroscopic bands. When the spectroscopic band occurs in the visible part of the electromagnetic spectrum, solvatochromism is observed as a change of colour. This is illustrated by Reichardt's dye, as shown in the image.

In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), or one in which light rays having different polarizations are absorbed by different amounts.

The International Colour Association (Association Internationale de la Couleur (AIC), or Internationale Vereinigung für die Farbe) is a learned society whose aims are to encourage research in all aspects of colour, to disseminate the knowledge gained from this research, and to promote its application to the solution of problems in the fields of science, art, design and industry on an international basis. The AIC also aims for a close cooperation with existing international organizations, such as, for example, the International Commission on Illumination (CIE), the International Organization for Standardization (ISO), and the International Commission for Optics (ICO), regarding issues concerned with colour. The AIC will neither duplicate the work of these bodies nor will it attempt to assume any of their responsibilities. In 2009 the AIC agreed on the creation of an International Colour Day, which is celebrated in many countries around the world.