Optics The meanings of the color terms violet and purple varies even among native speakers of English, for example between United Kingdom and United States. Optics research on purple and violet contains contributions of authors from different countries and different native languages, it is likely to be inconsistent in the use and meaning of the two colors. According to some speakers/authors of English, purple, unlike violet, is not one of the colors of the
visible spectrum. It was not one of the colors of the rainbow identified by
Isaac Newton. According to some authors, purple does not have its own
wavelength of light. For this reason, it is sometimes called a
non-spectral color. According to some speakers of English, purple is simply a combination, in various proportions, of two primary colors, red and blue. According to other speakers of English, the same range of colors is called violet. In some textbooks of
color theory, and depending on the geographical-cultural origin of the author, a "purple" is defined as any
non-spectral color between
violet and red (excluding violet and red themselves). However, also here there is much variation in color terminology depending on cultural background of the painters and authors, and sometimes the term violet is used and placed in between red and blue on the traditional color wheel. In a slightly different variation, on the
color wheel, purple is placed between magenta and violet. This shade is sometimes called electric purple (see
shades of purple). In the
RGB color model, named for the colors red, green, and blue, used to create all the colors on a computer screen or television, the range of purples is created by mixing red and blue light of different intensities on a black screen. The standard
HTML color purple is created by red and blue light of equal intensity, at a brightness that is between full power and darkness. In color printing, purple is sometimes represented by the color
magenta mixed with cyan or black or sometimes by mixing magenta with red or blue. It can also be created by mixing just red and blue alone, but in that case the purple is less bright, with lower saturation or intensity. A less bright purple can also be created with light or paint by adding a certain quantity of the third primary color (green for light or yellow for pigment).
Relationship with violet highlights the
line of purples at its base, running from the violet corner near the left to the red corner at the right. Purple is closely associated with
violet. In common usage, both refer to a variety of colors between blue and red in
hue. Historically, purple has tended to be used for redder hues and violet for bluer hues. In
optics, violet is a
spectral color; it refers to the color of any different single wavelength of light on the short wavelength end of the visible spectrum, between approximately 380 and 450 nanometers, whereas purple is the color of various combinations of red, blue, and violet light, File:RGB illumination.jpg|On a computer or television screen, purple colors are created by mixing red and blue light. This is called the
RGB color model. File:CIExy1931.png|The
CIE xy chromaticity diagram Pigments •
Hematite and
manganese are the oldest pigments used for the color purple. They were used by
Neolithic artists in the form of sticks, like charcoal, or ground and powdered and mixed with fat, and used as a paint. Hematite is a reddish
iron oxide which, when ground coarsely, makes a purple pigment. One such pigment is
caput mortuum, whose name is also used in reference to
mummy brown. The latter is another pigment containing hematite and historically produced with the use of mummified corpses. Some of its compositions produce a purple color and may be called "mummy violet". Manganese was also used in Roman times to color glass purple. •
Han purple was the first synthetic purple pigment, invented in China in about 700 BC. It was used in wall paintings and pottery and other applications. In color, it was very close to
indigo, which had a similar chemical structure. Han purple was very unstable, and sometimes was the result of the chemical breakdown of Han blue. During the Middle Ages, artists usually made purple by combining red and blue pigments; most often blue azurite or lapis-lazuli with
red ochre,
cinnabar, or
minium. They also combined lake colors made by mixing dye with powder; using
woad or indigo dye for the blue, and dye made from
cochineal for the red. •
Manganese violet was a stronger color than cobalt violet, and replaced it on the market. •
Quinacridone violet, one of a modern synthetic organic family of colors, was discovered in 1896 but not marketed until 1955. It is sold today under a number of brand names. File:Lascaux painting.jpg|
Manganese pigments were used in the
neolithic paintings in the
Lascaux cave, France. File:Hematite.jpg|
Hematite was often used as the red-purple color in the cave paintings of
Neolithic artists. File:Purpurite-120161.jpg|A sample of
purpurite, or manganese phosphate, from the Packrat Mine in Southern California. File:Cobaltviolet.jpg|A swatch of cobalt violet, popular among the French
impressionists. File:Manganese violet.jpg|
Manganese violet is a synthetic pigment invented in the mid-19th century. File:CI Pigment Violet 19 Beta.JPG|
Quinacridone violet, a synthetic organic pigment sold under many different names.
Dyes The most famous purple dye in the ancient world was
Tyrian purple, made from a type of sea snail called the
murex, found around the Mediterranean. (See history section above). In the Middle Ages, those who worked with blue and black dyes belonged to separate guilds from those who worked with red and yellow dyes, and were often forbidden to dye any other colors than those of their own guild. Most purple fabric was made by the dyers who worked with red, and who used dye from
madder or
cochineal, so medieval violet colors were inclined toward red.
Orcein, or
purple moss, was another common purple dye. It was known to the ancient Greeks and Hebrews, and was made from a Mediterranean
lichen called archil or dyer's moss (
Roccella tinctoria), combined with an
ammoniac, usually urine. Orcein began to achieve popularity again in the 19th century, when violet and purple became the color of demi-mourning, worn after a widow or widower had worn black for a certain time, before he or she returned to wearing ordinary colors. From the Middle Ages onward, purple dyes for the clothing of common people were often made from the
blackberry or other red fruit of the genus
rubus, or from the
mulberry. All of these dyes were more reddish than bluish, and faded easily with washing and exposure to sunlight. A popular new dye which arrived in Europe from the New World during the Renaissance was made from the wood of the
logwood tree (H
aematoxylum campechianum), which grew in Spanish Mexico. Depending on the different minerals added to the dye, it produced a blue, red, black or, with the addition of
alum, a purple color, it made a good color, but, like earlier dyes, it did not resist sunlight or washing. In the 18th century, chemists in England, France and Germany began to create the first synthetic dyes. Two synthetic purple dyes were invented at about the same time.
Cudbear is a
dye extracted from
orchil lichens that can be used to dye
wool and
silk, without the use of
mordant. Cudbear was developed by Dr Cuthbert Gordon of
Scotland: production began in 1758, The lichen is first boiled in a solution of
ammonium carbonate. The mixture is then cooled and
ammonia is added and the mixture is kept damp for 3–4 weeks. Then the lichen is dried and ground to powder. The manufacture details were carefully protected, with a ten-feet high wall being built around the manufacturing facility, and staff consisting of Highlanders sworn to secrecy.
French purple was developed in France at about the same time. The lichen is extracted by urine or ammonia. Then the extract is acidified, the dissolved dye precipitates and is washed. Then it is dissolved in ammonia again, the solution is heated in air until it becomes purple, then it is precipitated with
calcium chloride; the resulting dye was more solid and stable than other purples.
Cobalt violet is a synthetic pigment that was invented in the second half of the 19th century, and is made by a similar process as
cobalt blue,
cerulean blue and
cobalt green. It is the violet pigment most commonly used today by artists. In spite of its name, this pigment produces a purple rather than violet color. discovered
serendipitously in 1856. Its chemical name is 3-amino-2,±9-dimethyl-5-phenyl-7-(p-tolylamino)phenazinium acetate.
Fuchsine was another synthetic dye made shortly after mauveine. It produced a brilliant fuchsia color. In the 1950s, a new family of purple and violet synthetic organic pigments called
quinacridone came onto the market. It had originally been discovered in 1896, but were not synthesized until 1936, and not manufactured until the 1950s. The colors in the group range from deep red to bluish purple in color, and have the molecular formula C20H12N2O2. They have strong resistance to sunlight and washing, and are widely used today in oil paints, water colors, and acrylics, as well as in automobile coatings and other industrial coatings. File:Black Butte blackberry.jpg|
Blackberries were sometimes used to make purple dye in the Middle Ages. File:A lichen - Ochrolechia tartarea - geograph.org.uk - 995354.jpg|This lichen, growing on a tree in Scotland, was used in the 18th century to make a common purple dye called Cudbear. File:Mauv2.jpg|A sample of silk dyed with the original mauveine dye. File:Basic Fuchsine in aqueous solution.jpg|A sample of
fuchsine dye
Animals File:Cinnyricinclus_leucogaster_-_20080321.jpg|The male
violet-backed starling sports a very bright, iridescent purple plumage. File:Nasikabatrachus sahyadrensis.jpg|The
purple frog is a species of
amphibian found in India. File:Pseudanthias pascalus.jpg|
Pseudanthias pascalus or purple queenfish. File:PurpleUrchinPuertoVG.JPG|The
purple sea urchin from Mexico. File:Purple Heron in flight.jpg|A
purple heron in flight (South Africa). File:Carpodacus purpureus CT3.jpg|A
purple finch (North America). File:Lorius domicella -Jurong Bird Park -upper body-8a.jpg|The
Lorius domicella, or purple-naped lory, from Indonesia.
Anthocyanins Certain grapes, eggplants, pansies and other fruits, vegetables and flowers may appear purple due to the presence of natural pigments called
anthocyanins. These pigments are found in the leaves, roots, stems, vegetables, fruits and flowers of all plants. They aid
photosynthesis by blocking harmful wavelengths of light that would damage the leaves. In flowers, the purple anthocyanins help attract insects who pollinate the flowers. Not all anthocyanins are purple; they vary in color from red to purple to blue, green, or yellow, depending upon the level of their
pH. File:Purplec.png|The purple colors of this
cauliflower, grapes, fruits, vegetables and flowers comes from natural pigments called
anthocyanins. File:Indicateur chou rouge.jpg|Anthocyanins range in color from red to purple to green, blue and yellow, depending upon the level of their
pH. File:Img fagus sylvatica atropurpurea 1890.jpg|Anthocyanins also account for the purple color in these
copper beech trees, and in purple autumn leaves. File:Blood orange sliced.jpg|Anthocyanins produce the purple color in blood oranges. File:Purple pansy flower.jpg|alt=Purple pansy|A purple
pansy. File:Blue Hydrangea (common names hydrangea or hortensia).jpg|alt="Blue" hydrangea is often actually purple.|"Blue"
hydrangea is often actually purple.
Plants and flowers •
Purple needlegrass is the
state grass of California. File:Artichoke in Dalat, Vietnam.jpg|An
artichoke flower in blossom in Dalat,
Vietnam File:Iris germanica10.jpg|
Iris germanica flowers File:Lilac blossom Fliederblüte Syringa vulgaris 05.jpg|
Syringa vulgaris, or
lilac blossoms File:MEDICAGO SATIVA - APIS - IB-125.JPG|
Medicago sativa, known as
alfalfa in the U.S. and lucerne in the U.K. File:Aster alpinus 002.JPG|The
Aster alpinus, or alpine aster, is native to the European mountains, including the
Alps, while a subspecies is found in
Canada and the United States. File:Single lavender flower02.jpg|
Lavender flowers. File:Purple Rose1.jpg|A purple
rose. File:Wisteria floribunda5.jpg|alt=Wisteria is a pale purple color.|
Wisteria is a pale purple color. File:Purple_salsify_(7356683346).jpg|
salsify Microbiology •
Purple bacteria are
bacteria that are
phototrophic, that is, capable of producing energy through
photosynthesis. • In April 2007, it was suggested that early
archaea may have used
retinal, a purple pigment, instead of
chlorophyll, to extract energy from the sun. If so, large areas of the ocean and shoreline would have been colored purple; this is called the
Purple Earth hypothesis.
Astronomy • One of the
stars in the
Pleiades, called
Pleione, is sometimes called
Purple Pleione because, being a fast spinning star, it has a purple hue caused by its blue-white color being obscured by a spinning ring of electrically excited red
hydrogen gas. • The
Purple Forbidden enclosure is a name used in traditional
Chinese astronomy for those
Chinese constellations that surround the
north celestial pole.
Geography •
Purple Mountain is located on the eastern side of
Nanjing. Its peaks are often found enveloped in purple clouds at dawn and dusk, hence comes its name "Purple Mountain". The
Purple Mountain Observatory is located there. •
Purple Mountain in County Kerry, Ireland, takes its name from the color of the shivered slate on its summit. •
Purple Mountain in
Wyoming (el. ) is a mountain peak in the southern section of the
Gallatin Range in
Yellowstone National Park. • Purple Mountain, Alaska • Purple Mountain, Oregon • Purple Mountain, Washington • Purple Peak, Colorado File:Purple Mountain View, Killarney.jpg|
Purple Mountain near Killarney, Ireland. File:PurpleMountainYNP2010.jpg|
Purple Mountain in
Yellowstone National Park. File:南京人文之旅-紫金山天文台 - panoramio.jpg|
Purple Mountain, Nanjing.
Purple mountains phenomenon It has been observed that the greater the distance between a viewers eyes and mountains, the lighter and more blue or purple they will appear. This phenomenon, long recognized by
Leonardo da Vinci and other painters, is called
aerial perspective or atmospheric perspective. The more distant the mountains are, the less contrast the eye sees between the mountains and the sky. The bluish color is caused by an optical effect called
Rayleigh scattering. The sunlit sky is blue because
air scatters short-
wavelength light more than longer wavelengths. Since blue light is at the short wavelength end of the visible spectrum, it is more strongly scattered in the atmosphere than long wavelength red light. The result is that the human eye perceives blue when looking toward parts of the sky other than the sun. At sunrise and sunset, the light is passing through the atmosphere at a lower angle, and traveling a greater distance through a larger volume of air. Much of the green and blue is scattered away, and more red light comes to the eye, creating the colors of the sunrise and sunset and making the mountains look purple. The phenomenon is referenced in the song "
America the Beautiful", where the lyrics refer to "purple mountains' majesty" among other features of the United States landscape. A
Crayola crayon called Purple Mountain Majesty in reference to the lyric was first formulated in 1993. File:Aerial perspective 1.JPG|The more distant mountains are, the lighter and more blue they are. This is called atmospheric perspective or
aerial perspective. File:Auke Bay Alaska 2.jpg|Sunset at
Auke Bay,
Alaska. Thanks to
Rayleigh scattering, the mountains appear purple. == Mythology ==