Editing Color theory (section)

== Color mixing ==
{{Main|Color mixing}}
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One of the earliest purposes of color theory was to establish rules governing the mixing of pigments.

Traditional color theory was built around "pure" or ideal colors, characterized by different sensory experiences rather than attributes of the physical world. This has led to several inaccuracies in traditional color theory principles that are not always remedied in modern formulations.<ref>{{Cite web|title=handprint: colormaking attributes|url=https://www.handprint.com/HP/WCL/color6.html|access-date=2021-07-31|website=www.handprint.com}}</ref> Another issue has been the tendency to describe color effects holistically or categorically, for example as a contrast between "yellow" and "blue" conceived as generic colors instead of the three color attributes generally considered by color science: [[hue]], [[colorfulness]] and [[lightness]]. These confusions are partly historical and arose in scientific uncertainty about color perception that was not resolved until the late 19th century when artistic notions were already entrenched. They also arise from the attempt to describe the highly contextual and flexible behavior of color perception in terms of abstract color sensations that can be generated equivalently by any [[visual media]].{{Citation needed|date=September 2022}}

=== Primary colors ===
{{Main|Primary color}}
[[File:Color star-en (tertiary names).svg|thumb|Primary, secondary, and tertiary colors of the [[RYB color model]]]]

Color theory asserts three pure primary colors that can be used to mix all possible colors. These are sometimes considered as red, yellow and blue ([[RYB color model|RYB]]) or as red, green and blue ([[RGB color model|RGB]]).{{Citation needed|date=April 2024}} Ostensibly, any failure of specific [[paint]]s or [[ink]]s to match this ideal performance is due to the impurity or imperfection of the colorants. In contrast, modern color science does not recognize universal primary colors (no finite combination of colors can produce all other colors) and only uses primary colors to define a given [[color space]].<ref name="Handprint1"/> Any three primary colors can mix only a limited range of colors, called a [[gamut]], which is always smaller (contains fewer colors) than the full range of colors humans can perceive.<ref>{{Cite web|title=Traditional and Modern Colour Theory Part 1: Modern Colour Theory|url=http://www.huevaluechroma.com/112.php|access-date=2021-10-15|language=en-AU}}</ref> Primary colors also can't be made from other colors as they are inherently pure and distinct.<ref>{{Cite web|title=3 Basic Primary Colors {{!}} Additive and Subtractive Color Mixing|url=https://www.geeksforgeeks.org/primary-colors/|date=February 28, 2024 |access-date=2025-01-10|language=en-USA}}</ref>

=== Complementary colors ===
{{Main|Complementary colors}}
[[File:Chevreul's RYB chromatic diagram.png|upright=1.35|thumb|[[Michel Eugène Chevreul|Chevreul]]'s 1855 "chromatic diagram" based on the [[RYB color model]], showing [[complementary colors]] and other relationships]]

For the mixing of colored light, [[Isaac Newton]]'s [[color wheel]] is often used to describe complementary colors, which are colors that cancel each other's hue to produce an achromatic (white, gray or black) light mixture. Newton offered as a conjecture that colors exactly opposite one another on the hue circle cancel out each other's hue; this concept was demonstrated more thoroughly in the 19th century. An example of [[complementary colors]] would be magenta and green.{{citation needed|date=April 2024}}

A key assumption in Newton's hue circle was that the "fiery" or maximum saturated hues are located on the outer circumference of the circle, while achromatic white is at the center. Then the saturation of the mixture of two spectral hues was predicted by the straight line between them; the mixture of three colors was predicted by the "center of gravity" or centroid of three triangle points, and so on.

According to traditional color theory based on [[subtractive primary color]]s and the RYB color model, yellow mixed with purple, orange mixed with blue, or red mixed with green produces an equivalent gray and are the painter's complementary colors.

One reason the artist's primary colors work at all is due to the imperfect pigments being used have sloped absorption curves and change color with concentration. A pigment that is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. [[Chromium]] red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and the chromium red to get a greenish color. This works much better with oil colors than it does with watercolors and dyes.

The old primaries depend on sloped [[Absorption spectroscopy|absorption]] curves and pigment leakages to work, while newer scientifically derived ones depend solely on controlling the amount of absorption in certain parts of the [[spectrum]].

=== Tints and shades ===
{{Main|Tint, shade and tone}}

When mixing pigments, a color is produced which is always darker and lower in chroma, or saturation, than the parent colors. This moves the mixed color toward a neutral color—a gray or near-black. Lights are made brighter or dimmer by adjusting their brightness, or energy level; in painting, lightness is adjusted through mixture with white, black, or a color's complement.

It is common among some painters to darken a paint color by adding black paint—producing colors called ''shades''—or lighten a color by adding white—producing colors called ''tints''. However, it is not always the best way for representational painting, as an unfortunate result is for colors to also shift in hue. For instance, darkening a color by adding black can cause colors such as yellows, reds, and oranges, to shift toward the greenish or bluish part of the spectrum. Lightening a color by adding white can cause a shift towards blue when mixed with reds and oranges. Another practice when darkening a color is to use its opposite, or complementary, color (e.g. purplish-red added to yellowish-green) to neutralize it without a shift in hue and darken it if the additive color is darker than the parent color. When lightening a color this hue shift can be corrected with the addition of a small amount of an adjacent color to bring the hue of the mixture back in line with the parent color (e.g. adding a small amount of orange to a mixture of red and white will correct the tendency of this mixture to shift slightly towards the blue end of the spectrum).

=== Split primary palette ===
The split-primary palette is a color-wheel model that relies on misconceptions to attempt to explain the unsatisfactory results produced when mixing the traditional primary colors, red, yellow, and blue.

Painters have long considered red, yellow, and blue to be primary colors. In practice, however, some of the mixtures produced from these colors lack [[Colorfulness|chromatic intensity]]. Rather than adopt a [[CMY color model|more effective set of primary colors]],<ref>{{cite web |last1=Baird |first1=Christopher S. |title=Associate Professor of Physics |url=https://www.wtamu.edu/~cbaird/sq/2015/01/22/why-are-red-yellow-and-blue-the-primary-colors-in-painting-but-computer-screens-use-red-green-and-blue/ |website=Science Questions with Surprising Answers |publisher=West Texas A&M University |access-date=12 June 2024}}</ref> proponents of split-primary theory explain this lack of chroma by the purported presence of impurities, small amounts of other colors in the paints, or biases away from the ideal primary toward one or the other of the adjacent colors. Every red paint, for example, is said to be tainted with, or biased toward, either blue or yellow, every blue paint toward either red or green, and every yellow toward either green or orange. These biases are said to result in mixtures that contain sets of [[complementary colors]], darkening the resulting color. To obtain vivid mixed colors, according to split-primary theory, it is necessary to employ two primary colors whose biases both fall in the direction, on the color wheel, of the color to be mixed, combining, for example, green-biased blue and green-biased yellow to make bright green. Based on this reasoning, proponents of split-primary theory conclude that two versions of each primary color, often called "cool" and "warm," are needed in order to mix a wide [[gamut]] of high-chroma colors.<ref>{{cite web |last1=Kemp |first1=Will |title=The Hidden Hues of Colour Mixing |url=https://willkempartschool.com/the-hidden-secret-of-colour-mixing/ |website=willkempartschool.com |date=27 August 2011 |publisher=Will Kemp Art School |access-date=15 October 2023}}</ref><ref>{{cite web |last1=Short |first1=Susie |title=Working with a Split Primary Color Palette |url=https://danielsmith.com/artists/insights/susie-short-working-with-a-split-primary-color-palette/ |website=danielsmith.com |date=21 July 2022 |publisher=Daniel Smith |access-date=15 October 2023}}</ref>

In fact, the perceived bias of colors is not due to impurity. Rather, the appearance of any given colorant is inherent to its chemical and physical properties, and its purity unrelated to whether it conforms to our arbitrary conception of an ideal hue. Moreover, the identity of gamut-optimizing primary colors is determined by the physiology of [[Trichromacy|human color vision]]. Although no set of three primary paints can be mixed to obtain the complete color gamut perceived by humans, red, yellow, and blue are a poor choice if high-chroma mixtures are desired. This is because painting is a [[subtractive color]] process, for which red and blue are secondary, not primary, colors.

Although flawed in principle,<ref>{{cite web |last1=Lucariello |first1=Joan |last2=Naff |first2=David |title=How Do I Get My Students Over Their Alternative Conceptions (Misconceptions) for Learning? Applications of Psychological Science to Teaching and Learning modules |url=https://www.apa.org/education-career/k12/misconceptions |website=APA.org |publisher=American Psychological Association |access-date=12 August 2024}}</ref> the split-primary system can be successful in practice, because the recommended blue-biased red and green-biased blue positions are often filled by near approximations of magenta and cyan, respectively, while orange-biased red and violet-biased blue serve as secondary colors, tending to further widen the mixable gamut.

This system is in effect a simplified version of Newton's geometrical rule that colors closer together on the hue circle will produce more vibrant mixtures.  A mixture produced from two primary colors, however, will be much more highly saturated than one produced from two secondary colors, even though the pairs are the same distance apart on the hue circle, revealing the limitations of the circular model in the prediction of color-mixing results. For example, a mixture of magenta and cyan inks or paints will produce vivid blues and violets, whereas a mixture of red and blue inks or paints will produce darkened violets and purples, even though the angular distance separating magenta and cyan is the same as that separating red and blue.