Editing Natural Color System (section)

== Comparisons to other color systems ==
The most important difference between NCS and most other color systems resides in their starting points. The aim of NCS is to define colors from their visual appearance, as they are experienced by human consciousness. Other color models, such as [[CMYK color model|CMYK]] and [[RGB color model|RGB]], are based on an understanding of physical processes, how colors can be achieved or "made" in different media.<ref>{{Cite journal|title = The Value of Knowledge for Color Design|last = Green-Armytage|first = Paul|date = 2006|journal = Color Research and Application|volume = 31|issue = 31:4|pages = 253–269|doi = 10.1002/col.20222}}</ref>

According to the opponent process hypothesis, the underlying physiological mechanisms involved in color opponency include the [[bipolar cell|bipolar]] and [[Retinal ganglion cell|ganglion cell]]s in the [[retina]], which process the signal originated by the retinal [[cone cell|cones]] before it is sent to the [[brain]]. Models like [[RGB color model|RGB]] are based<!-- this is correct. XYZ (not RGB) _describes_ it --> on what happens at the lower, retinal cone level, and thus are fitted for presenting self-illuminated, dynamic images as done by [[Television set|TV sets]] and [[computer display]]s; see [[additive color]]. The NCS model, for its part, describes the organization of the color sensations as perceived at the upper, brain level, and thus is much better fitted than RGB to deal with how humans experience and describe their color sensations (hence the "natural" part of its name). More problematic is the relation with the CMYK-model which is generally seen as a correct prediction of the behavior of [[color mixing|mixing pigments]], as a system of [[subtractive color]]. The NCS coincides with the CMYK as regards the green-yellow-red segment of the [[color circle]], but differs from it in seeing the saturated subtractive [[primary color]]s [[magenta]] and [[cyan]] as complex sensations of a "redblue" and a "greenblue" respectively and in seeing green, not as a [[secondary color]] mix of yellow and cyan, but as a unique hue. The NCS explains this by assuming that the behavior of paint is partly counterintuitive to human phenomenology. Observing that the mix of yellow and "greenblue" (cyan) paint results in a green color, would thus be at odds with the intuition of human perception, because green would be perceived as an elementary hue while yellow and the presumed blue component of "greenblue" are by the NCS considered to be mutually excluding percepts.

Hering argued that yellow is not a "redgreen" but a unique hue. [[Colorimetry|Colorimetrist]] [[Jan Koenderink]], in a critique of Hering's system, considered it inconsistent not to apply the same argument to the other two subtractive primaries (or additive secondaries), cyan and magenta, and see them as unique hues as well, not a "greenblue" or a "redblue". He also pointed out the difficulty within a four-color theory that the primaries would not be equally spaced in the color circle; and the problem that Hering does not account for the fact that cyan and magenta are lighter than green, blue and red, whereas this is, in his view, elegantly explained within the CMYK-model. He concluded that Hering's scheme fitted common language better than color experience.<ref>[[Jan Koenderink|Jan J. Koenderink]], 2010, ''Color for the Sciences'', The MIT Press, pp. 579–582</ref>

Overview of the six base colors in Natural Colour System with their equivalent in hex triplet, RGB and HSV coordinates systems. However, note that these codes are only approximate, as the definition of NCS elementaries is based on perception and not production of color.

:{| class="wikitable"
|+ NCS base colors
!colspan=2 | Color !!colspan=3| [[RGB color model|RGB]] !!colspan=3| [[HSL and HSV|HSV]]
|-
|style="background:#FFF;color:#FFF;width:16px"| FFFFFF || White (#FFFFFF) || 100% || 100% || 100% || — || 0% || 100%
|-
|style="background:#000;color:#000"| 000000 || Black (#000000) || 0% || 0% || 0% || — || — || 0%
|-
|style="background:#009f6b;color:#009F6B"| 009F6B || Green (#009F6B) || 0% || 62% || 42% || 160° || 100% || 63%
|-
|style="background:#C40233;color:#C40233"| C40233  || Red (#C40233) || 77% || 1% || 20% || 345° || 99% || 77%
|-
|style="background:#FFD300;color:#FFD300"| FFD300 || Yellow (#FFD300) || 100% || 83% || 0% || 50° || 100% || 100%
|-
|style="background:#0087BD;color:#0087BD"| 0087BD  || Blue (#0087BD) || 0% || 53% || 74% || 197° || 100% || 74%
|}