Editing Color (section)

=== Nonstandard color perception<span class="anchor" id="Nonstandard colour perception"></span> ===

==== Color vision deficiency<span class="anchor" id="Colour vision deficiency"></span> ====
{{main|Color blindness}}
A color vision deficiency causes an individual to perceive a smaller [[gamut]] of colors than the standard observer with normal color vision. The effect can be mild, having lower "color resolution" (i.e. [[anomalous trichromacy]]), moderate, lacking an entire dimension or channel of color (e.g. [[dichromacy]]), or complete, lacking all color perception (i.e. [[monochromacy]]). Most forms of color blindness derive from one or more of the three classes of cone cells either being missing, having a shifted [[spectral sensitivity]] or having lower responsiveness to incoming light. In addition, [[cerebral achromatopsia]] is caused by neural anomalies in those parts of the brain where visual processing takes place.

Some colors that appear distinct to an individual with normal color vision will appear [[metamerism (color)|metameric]] to the color blind. The most common form of color blindness is [[congenital red–green color blindness]], affecting ~8% of males. Individuals with the strongest form of this condition ([[dichromacy]]) will experience blue and purple, green and yellow, teal, and gray as colors of confusion, i.e. metamers.<ref>{{cite web |last1=Flück |first1=Daniel |title=Colorblind colors of confusion |url=https://www.color-blindness.com/2009/01/19/colorblind-colors-of-confusion/ |website=Colblindor |date=19 January 2009 |access-date=14 November 2022}}</ref>

==== Tetrachromacy ====
{{main|Tetrachromacy}}
Outside of humans, which are mostly ''trichromatic'' (having three types of cones), most mammals are dichromatic, possessing only two cones. However, outside of mammals, most vertebrates are ''[[tetrachromatic]]'', having four types of cones. This includes most [[bird]]s,<ref>{{cite journal |last1=Bennett |first1=Andrew T. D. |last2=Cuthill |first2=Innes C. |last3=Partridge |first3=Julian C. |last4=Maier |first4=Erhard J. |year=1996 |title=Ultraviolet vision and mate choice in zebra finches |journal=Nature |volume=380 |issue=6573 |pages=433–435 |bibcode=1996Natur.380..433B |doi=10.1038/380433a0 |s2cid=4347875}}</ref><ref>{{cite journal |last1=Bennett |first1=Andrew T. D. |last2=Théry |first2=Marc |year=2007 |title=Avian Color Vision and Coloration: Multidisciplinary Evolutionary Biology |url=https://hal.archives-ouvertes.fr/hal-02889396/file/Bennett%20%26%20Thery%20Am%20Nat%202007.pdf |journal=The American Naturalist |volume=169 |issue=S1 |pages=S1–S6 |doi=10.1086/510163 |issn=0003-0147 |jstor=510163 |bibcode=2007ANat..169S...1B |s2cid=2484928}}</ref><ref>{{cite book |last1=Cuthill |first1=Innes C. |title=Ultraviolet Vision in Birds |last2=Partridge |first2=Julian C. |last3=Bennett |first3=Andrew T. D. |last4=Church |first4=Stuart C. |last5=Hart |first5=Nathan S. |last6=Hunt |first6=Sarah |date=2000 |publisher=Academic Press |isbn=978-0-12-004529-7 |editor1-last=J. B. Slater |editor1-first=Peter |series=Advances in the Study of Behavior |volume=29 |page=159 |doi=10.1016/S0065-3454(08)60105-9 |editor2-last=Rosenblatt |editor2-first=Jay S. |editor3-last=Snowdon |editor3-first=Charles T. |editor4-last=Roper |editor4-first=Timothy J.}}</ref> [[reptile]]s, [[amphibian]]s, and [[teleost|bony fish]].<ref name="Bowm1">{{cite journal |last1=Bowmaker |first1=James K. |date=September 2008 |title=Evolution of vertebrate visual pigments |journal=Vision Research |volume=48 |issue=20 |pages=2022–2041 |doi=10.1016/j.visres.2008.03.025 |pmid=18590925 |s2cid=52808112 |doi-access=free}}</ref><ref>{{cite journal |last=Vorobyev |first=M. |date=November 1998 |title=Tetrachromacy, oil droplets and bird plumage colours |journal=Journal of Comparative Physiology A |volume=183 |issue=5 |pages=621–33 |doi=10.1007/s003590050286 |pmid=9839454 |s2cid=372159}}</ref> An extra dimension of color vision means these vertebrates can see two distinct colors that a normal human would view as [[metamerism (color)|metamer]]s. Some invertebrates, such as the [[mantis shrimp]], have an even higher number of cones (12) that could lead to a richer color [[gamut]] than even imaginable by humans.

The existence of human tetrachromats is a contentious notion. As many as [[tetrachromacy#Tetrachromacy in carriers of CVD|half of all human females have 4 distinct cone classes]], which could enable tetrachromacy.<ref name="Jameson">{{cite journal|last1=Jameson|first1=K.A.|last2=Highnote|first2=S.M.|last3=Wasserman|first3=L.M.|year=2001|title=Richer color experience in observers with multiple photopigment opsin genes.|doi=10.3758/BF03196159|journal=Psychonomic Bulletin and Review|volume=8|issue=2|pages=244–261 [256]|url=https://link.springer.com/content/pdf/10.3758/BF03196159.pdf |archive-url=https://web.archive.org/web/20131004220637/http://link.springer.com/content/pdf/10.3758/BF03196159.pdf |archive-date=2013-10-04 |url-status=live|pmid=11495112|s2cid=2389566|doi-access=free}}</ref> However, a distinction must be made between ''retinal'' (or ''weak'') ''tetrachromats'', which express four cone classes in the retina, and ''functional'' (or ''strong'') ''tetrachromats'', which are able to make the enhanced color discriminations expected of tetrachromats. In fact, there is only one peer-reviewed report of a functional tetrachromat.<ref>{{cite journal|last1=Jordan|first1=G.|last2=Deeb|first2=S.S.|last3=Bosten|first3=J.M.|last4=Mollon|first4=J.D.|title=The dimensionality of color vision in carriers of anomalous trichromacy|journal=Journal of Vision|date=20 July 2010|volume=10|issue=8|page=12|doi=10.1167/10.8.12|pmid=20884587|doi-access=free}}</ref> It is estimated that while the average person is able to see one&nbsp;million colors, someone with functional tetrachromacy could see a hundred&nbsp;million colors.<ref>{{cite web|last=Kershner|first=Kate|title=Lucky Tetrachromats See World With Up to 100 Million Colors|date=26 July 2016|url=https://science.howstuffworks.com/lucky-tetrachromats-see-world-100-million-colors.htm|access-date=9 February 2022}}</ref>

==== Synesthesia ====
{{main|Synesthesia}}

In certain forms of [[synesthesia]], perceiving letters and numbers ([[grapheme–color synesthesia]]) or hearing sounds ([[chromesthesia]]) will evoke a perception of color. Behavioral and [[functional neuroimaging]] experiments have demonstrated that these color experiences lead to changes in behavioral tasks and lead to increased activation of brain regions involved in color perception, thus demonstrating their reality, and similarity to real color percepts, albeit evoked through a non-standard route. Synesthesia can occur genetically, with 4% of the population having variants associated with the condition. Synesthesia has also been known to occur with brain damage, drugs, and sensory deprivation.<ref>{{cite journal|last1=Brang|first1=David|title=Survival of the Synesthesia Gene: Why Do People Hear Colors and Taste Words?|journal=PLOS Biology|date=22 November 2011|volume=9|issue=11|pages=e1001205|doi=10.1371/journal.pbio.1001205|pmid=22131906|pmc=3222625|doi-access=free}}</ref>

The philosopher Pythagoras experienced synesthesia and provided one of the first written accounts of the condition in approximately 550&nbsp;BCE. He created mathematical equations for musical notes that could form part of a scale, such as an octave.<ref>{{cite web|title=A Brief History of Synesthesia in the Arts|url=http://www.daysyn.com/history.html|access-date=9 February 2022}}</ref>