Gray Color in sciences and nature

Gray is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is a color “without color.” It is the color of a cloud-covered sky, of ash and of lead.

The first recorded use of grey as a color name in the English language was in AD 700. Grey is the dominant spelling in European and Commonwealth English, although gray remained in common usage in the UK until the second half of the 20th century. Gray has been the preferred American spelling since approximately 1825, although grey is an accepted variant.

In Europe and the United States, surveys show that grey is the color most commonly associated with neutrality, conformity, boredom, uncertainty, old age, indifference, and modesty. Only one percent of respondents chose it as their favorite color.

In the sciences, nature, and technology

Storm clouds
The whiteness or darkness of clouds is a function of their depth. Small, fluffy white clouds in summer look white because the sunlight is being scattered by the tiny water droplets they contain, and that white light comes to the viewer’s eye. However, as clouds become larger and thicker, the white light cannot penetrate through the cloud, and is reflected off the top. Clouds look darkest grey during thunderstorms, when they can be as much as 20,000 to 30,000 feet high.

Stratiform clouds are a layer of clouds that covers the entire sky, and which have a depth of between a few hundred to a few thousand feet thick. The thicker the clouds, the darker they appear from below, because little of the sunlight is able to pass through. From above, in an airplane, the same clouds look perfectly white, but from the ground the sky looks gloomy and grey.

The greying of hair
The color of a person’s hair is created by the pigment melanin, found in the core of each hair. Melanin is also responsible for the color of the skin and of the eyes. There are only two types of pigment; dark (eumelanin) or light (phaeomelanin). Combined in various combinations, these pigments create all natural hair colors.

Melanin itself is the product of a specialized cell, the melanocyte, which is found in each hair follicle, from which the hair grows. As hair grows, the melanocyte injects melanin into the hair cells, which contain the protein keratin and which makes up our hair, skin, and nails. As long as the melanocytes continue injecting melanin into the hair cells, the hair retains its original color. At a certain age, however, which varies from person to person, the amount of melanin injected is reduced and eventually stops. The hair, without pigment, turns grey and eventually white. The reason for this decline of production of melanocytes is uncertain. In the February 2005 issue of Science, a team of Harvard scientists suggested that the cause was the failure of the melanocyte stem cells to maintain the production of the essential pigments, due to age or genetic factors, after a certain period of time. For some people, the breakdown comes in their twenties; for others, many years later. According to the site of the magazine Scientific American, “Generally speaking, among Caucasians 50 percent are 50 percent grey by age 50.” Adult male gorillas also develop silver hair but only on their backs, see Physical characteristics of gorillas.

Over the centuries, artists have traditionally created grey by mixing black and white in various proportions. They added a little red to make a warmer grey, or a little blue for a cooler grey. Artists could also make a grey by mixing two complementary colors, such as orange and blue.

Today the grey on televisions, computer displays and telephones is usually created using the RGB color model. Red, green, and blue light combined at full intensity on the black screen makes white; by lowering the intensity, it is possible to create different shades of grey.

In printing, grey is usually obtained with the CMYK color model, using cyan, magenta, yellow and black. Grey is produced either by using black and white, or by combining equal amounts of cyan, magenta and yellow. Most greys have a cool or warm cast to them, as the human eye can detect even a minute amount of color saturation. Yellow, orange, and red create a “warm grey”. Green, blue, and violet create a “cool grey”. When no color is added, the color is “neutral grey”, “achromatic grey” or simply “grey”. Images consisting wholly of black, white and greys are called monochrome, black-and-white or greyscale.

Warm grey Cool grey
Mixed with 6% yellow. Mixed with 6% blue.

RGB model
Grey values result when r = g = b, for the color (r, g, b)
CMYK model
Grey values are produced by c = m = y = 0, for the color (c, m, y, k). Lightness is adjusted by varying k. In theory, any mixture where c = m = y is neutral, but in practice such mixtures are often a muddy brown (see discussion on this topic).

HSL and HSV model
Achromatic greys have no hue, so the h code is marked as “undefined” using a dash: — ; greys also result whenever s is 0 or undefined, as is the case when v is 0 or l is 0 or 1

HTML Color Name Sample Hex triplet
(rendered by name) (rendered by hex triplet)
gainsboro #DCDCDC
lightgray #D3D3D3
silver #C0C0C0
darkgray #A9A9A9
gray #808080
dimgray #696969
lightslategray #778899
slategray #708090
darkslategray #2F4F4F

Web colors
There are several tones of grey available for use with HTML and Cascading Style Sheets (CSS) as named colors, while 254 true greys are available by specification of a hex triplet for the RGB value. All are spelled gray, using the spelling grey can cause errors. This spelling was inherited from the X11 color list. Internet Explorer’s Trident browser engine does not recognize grey and renders it green. Another anomaly is that gray is in fact much darker than the X11 color marked darkgray; this is because of a conflict with the original HTML gray and the X11 gray, which is closer to HTML’s silver. The three slategray colors are not themselves on the greyscale, but are slightly saturated towards cyan (green + blue). Since there are an even (256, including black and white) number of unsaturated tones of grey, there are two grey tones straddling the midpoint in the 8-bit greyscale. The color name gray has been assigned the lighter of the two shades (128, also known as #808080), due to rounding up.

Until the 19th century, artists traditionally created grey by simply combining black and white. Rembrandt Van Rijn, for instance, usually used lead white and either carbon black or ivory black, along with touches of either blues or reds to cool or warm the grey.

In the early 19th century, a new grey, Payne’s grey, appeared on the market. Payne’s grey is a dark blue-grey, a mixture of ultramarine and black or of ultramarine and Sienna. It is named after William Payne, a British artist who painted watercolors in the late 18th century. The first recorded use of Payne’s grey as a color name in English was in 1835.

Animal color
Grey is a very common color for animals, birds and fish, ranging in size from whales to mice. It provides a natural camouflage and allows them to blend with their surroundings.

Grey matter of the brain
The substance that composes the brain is sometimes referred to as grey matter, or “the little grey cells”, so the color grey is associated with things intellectual. However, the living human brain is actually pink in color; it only turns grey when dead.

Nanotechnology and grey goo
Grey goo is a hypothetical end-of-the-world scenario, also known as ecophagy: out-of-control self-replicating nanobots consume all living matter on Earth while building more of themselves.

Grey noise
In sound engineering, grey noise is random noise subjected to a psychoacoustic equal loudness curve, such as an inverted A-weighting curve, over a given range of frequencies, giving the listener the perception that it is equally loud at all frequencies.

Source From Wikipedia