Storm clouds , Ireland 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.
Optics 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
azure. 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 all the different
shades of grey. In printing, grey is usually obtained with the
CMYK color model. By using black ink at a lower density than the one needed to print black, all the shades of grey can be created. Grey can also be formed by mixing cyan, magenta, and yellow in a specific proportion, each at a low or moderate density. Usually, both methods are combined. Most greys have a cool or a warm cast to them, as the
human eye can detect even a minute amount of color saturation. Adding a small amount of yellow, orange, or red will create a "warm grey". Adding a small amount of green, cyan, blue, or
violet will form 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. ;
RGB model : Grey values result when
R =
G =
B, for the color (
R, G, B) (0 < R, G, B < 1). : ;
CMYK model : Grey values are produced by
C = M = Y = 0; 0 < K < 1, 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. : ;
HSL and HSV models:Achromatic greys have no saturation, so grey is produced by S = 0; 0 < (L or V) < 1; (hue (H) is undefined), for the color (H, S, L) or (H, S, V).
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 grey and the X11 grey, which is closer to HTML's
silver. The three
slategray colors are not themselves on the greyscale, but are slightly
saturated toward
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.
Pigments 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 an
equal-loudness contour, 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. ==In culture==