question: How can the color spectrum be wrapped into a continuous color wheel? How can the highest frequency colors blend into the lowest frequency colors without clashing?
comment: Because our eyes only detect three colours of light: red, green, and blue. When both red and blue light reaches our eyes but not green, we perceive it as magenta (a bright pinkish purple color). When both red and green light reaches out eyes but not blue, we perceive it as yellow - but what is interesting is that things that reflect *yellow light* will stimulate both our red and green receptors as well (just not *as much* for the red receptor as red light would) so yellow light also stimulates the red and green detectors, hence why it looks yellow. In short, there are two ways to see yellow - from actual yellow light (which is between the wavelengths most detected by the red and the green receptors) and also from a little bit of red light and a little bit of green light both being detected at the same time. But there is only one way to detect magenta, since there's no magenta wavelength! The wavelength between red and blue is just the green wavelength, but if you are detecting both red and blue but *not* green, it can't be a really bright green spilling into red and blue! So it must be something else. As such, our minds blend the colours smoothly as we add or remove various amounts of each colour, and this necessitates a ring-like structure.
passages: The characteristic colors are, from long to short wavelengths (and, correspondingly, from low to high frequency), red, orange, yellow, green, blue, and violet. Sufficient differences in wavelength cause a difference in the perceived hue; the just-noticeable difference in wavelength varies from about 1 nm in the blue-green and yellow wavelengths, to 10 nm and more in the longer red and shorter blue wavelengths. Although the human eye can distinguish up to a few hundred hues, when those pure spectral colors are mixed together or diluted with white light, the number of distinguishable chromaticities can be quite high.
   This system implies that for any hue or non-spectral color not on the boundary of the chromaticity diagram, there are infinitely many distinct physical spectra that are all perceived as that hue or color. So, in general there is no such thing as "the" combination of spectral colors that we perceive as (say) a specific version of tan; instead there are infinitely many possibilities that produce that exact color. The boundary colors that are pure spectral colors can be perceived only in response to light that is purely at the associated wavelength, while the boundary colors on the "line of purples" can each only be generated by a specific ratio of the pure violet and the pure red at the ends of the visible spectral colors.
   Section::::Opponent process.
  
  The color opponent process is a color theory that states that the human visual system interprets information about color by processing signals from cone and rod cells in an antagonistic manner. The three types of cone cells have some overlap in the wavelengths of light to which they respond, so it is more efficient for the visual system to record differences between the responses of cones, rather than each type of cone's individual response. The opponent color theory suggests that there are three opponent channels:
  
  BULLET::::- Red versus green.
  
  BULLET::::- Blue versus yellow
   Section::::Physiology of color perception.:Cone cells in the human eye.
  
  A range of wavelengths of light stimulates each of these receptor types to varying degrees. The brain combines the information from each type of receptor to give rise to different perceptions of different wavelengths of light.
   Vision in humans is due to a system that starts with rods and cones photoreceptors, passes through retinal ganglion cells and arrives in the brain visual cortex. Color vision is achieved through cone cells, each one able to distinguish between a continuous band of frequencies, retinal ganglion cells and the visual cortex.
   The response curve as a function of wavelength varies for each type of cone. Because the curves overlap, some tristimulus values do not occur for any incoming light combination. For example, it is not possible to stimulate "only" the mid-wavelength (so-called "green") cones; the other cones will inevitably be stimulated to some degree at the same time. The set of all possible tristimulus values determines the human "color space". It has been estimated that humans can distinguish roughly 10 million different colors.
   However, light in the natural world is almost never purely monochromatic; most natural light sources and reflected light from natural objects comprise spectra that have complex profiles, with varying power over many different frequencies. A naive perspective might be that therefore all these different complex spectra would generate color perceptions completely different from those evoked in the rainbow of pure spectral light. One can perhaps see intuitively that this is not correct: almost all hues in the natural world (purples being the exception, see below) are represented in the pure rainbow spectrum, although they may be darker or less saturated than they appear in the rainbow. How is it that all the complex spectra in the natural world can be condensed to hues in the rainbow, which only represents simple monochromatic band peak spectra? This is the result of the design of the eye: the three color photoreceptors in the retina (the cones) reduce the information in the light spectrum down to three activity coordinates. Thus, many different physical light spectra converge psychologically to the same perceived color. In effect, for any single color perception, there is a whole parametric space in the power/frequency domain that maps to that one color.
   Most of the colors listed do not reach the maximal (spectral) colorfulness, or are not usually seen with it, but they can be saturated enough to be perceived closely to their dominant wavelength spectral colors. Ranges of wavelengths and frequencies are only approximate.
  
  Wavelengths and frequencies in gray indicate dominant wavelengths and frequencies, not actual range of spectrum composing a specified color, which extends farther to both sides and is averaged by receptors to give a near-spectral appearance.
  
  Section::::Non-spectral colors.
  
  Among some of the colors that are spectral colors are:
  
  BULLET::::- Grayscale (achromatic) colors, such as white, gray, and black.
   The normal three kinds of light-sensitive photoreceptor cells in the human eye (cone cells) respond most to yellow (long wavelength or L), green (medium or M), and violet (short or S) light (peak wavelengths near 570 nm, 540 nm and 440 nm, respectively). The difference in the signals received from the three kinds allows the brain to differentiate a wide gamut of different colors, while being most sensitive (overall) to yellowish-green light and to differences between hues in the green-to-orange region.
   Systems that use additive color processes usually have a color gamut which is roughly a convex polygon in the hue-saturation plane. The vertices of the polygon are the most saturated colors the system can produce. In subtractive color systems, the color gamut is more often an irregular region.
  
  Section::::Comparison of various systems.
  
  Following is a list of representative color systems more-or-less ordered from large to small color gamut:
   Section::::Spectral colors.
  
  Colors that can be produced by visible light of a narrow band of wavelengths (monochromatic light) are called pure spectral colors. The various color ranges indicated in the illustration are an approximation: The spectrum is continuous, with no clear boundaries between one color and the next.
  
  Section::::Color display spectrum.
   Subtractive color
  
  Subtractive color, or "subtractive color mixing", predicts the spectral power distribution of light after it passes through successive layers of partially absorbing media. This idealized model is the essential principle of how dyes and inks are used in color printing and photography where the perception of color is elicited after white light passes through microscopic "stacks" of partially absorbing media allowing some wavelengths of light to reach the eye and not others.
  
  Section::::RYB.
   Since each wavelength "w" stimulates each of the 3 types of cone cells to a known extent, these extents may be represented by 3 functions "s"("w"), "m"("w"), "l"("w") corresponding to the response of the "S", "M", and "L" cone cells, respectively.
   Because of this, and because the "primaries" in [[color printing]] systems generally are not pure themselves, the colors reproduced are never perfectly saturated spectral colors, and so spectral colors cannot be matched exactly. However, natural scenes rarely contain fully saturated colors, thus such scenes can usually be approximated well by these systems. The range of colors that can be reproduced with a given color reproduction system is called the [[gamut]]. The [[International Commission on Illumination|CIE]] chromaticity diagram can be used to describe the gamut.
   BULLET::::1. Colors that would be seen if the output strengths of the human eye retina's three types of cone cell (red, green, blue) could be set to values which cannot be produced by exposing the eye in normal seeing conditions to any possible combination of strengths of the frequencies of visible light.
   Section::::Source SPD and color appearance.
  
  The human visual response relies on trichromacy to process color appearance. While the human visual response integrates over all wavelengths, the relative spectral power distribution will provide color appearance modeling information as the concentration of wavelength band(s) will become the primary contributors to the perceived color.
  
  This becomes useful in photometry and colorimetry as the perceived color changes with source illumination and spectral distribution and coincides with metamerisms where an object's color appearance changes.
   As an example, suppose that light in the orange range of wavelengths (approximately 577 nm to 597 nm) enters the eye and strikes the retina. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more. The difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the orange appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously but to different degrees.
   Section::::Conversion xyY color system.
   Below is a rough table of wavelengths, colors and complementary colors. This utilizes the scientific CMY and RGB color wheels rather than the traditional RYB color wheel.
  
  This can only be used as a very rough guide, for instance if a narrow range of wavelengths within the band 647-700 is absorbed, then the blue and green receptors will be fully stimulated, making cyan, and the red receptor will be partially stimulated, diluting the cyan to a greyish hue.
  
  Section::::By category.
   Section::::Method.:Simple color function.
  
  The following example colors the origin in black, in red, in cyan, and a point at infinity in white:
  
  where formula_5.
  
  More precisely, it uses the HLS (hue, lightness, saturation) color model. Saturation is always set at the maximum of 100%. Vivid colors of the rainbow are rotating in a continuous way on the complex unit circle, so the sixth roots of unity (starting with 1) are: red, yellow, green, cyan, blue, and magenta. Magnitude is coded by intensity via a strictly monotonic continuous function. 
   Section::::Direct color.:High dynamic range and wide gamut.
   The ability of the [[human eye]] to distinguish colors is based upon the varying sensitivity of different cells in the [[retina]] to light of different [[wavelengths]]. Humans are [[Trichromacy|trichromatic]]—the retina contains three types of color receptor cells, or [[cone cell|cones]]. One type, relatively distinct from the other two, is most responsive to light that is perceived as blue or blue-violet, with wavelengths around 450 [[nanometre|nm]]; cones of this type are sometimes called "short-wavelength cones", "S cones", or "blue cones". The other two types are closely related genetically and chemically: "middle-wavelength cones", "M cones", or "green cones" are most sensitive to light perceived as green, with wavelengths around 540 nm, while the "long-wavelength cones", "L cones", or "red cones", are most sensitive to light is perceived as greenish yellow, with wavelengths around 570  nm.
   No mixture of colors, however, can produce a response truly identical to that of a spectral color, although one can get close, especially for the longer wavelengths, where the [[CIE 1931 color space]] chromaticity diagram has a nearly straight edge. For example, mixing green light (530 nm) and blue light (460 nm) produces cyan light that is slightly desaturated, because response of the red color receptor would be greater to the green and blue light in the mixture than it would be to a pure cyan light at 485 nm that has the same intensity as the mixture of blue and green.
   Each of the three types of cones in the retina of the eye contains a different type of photosensitive pigment, which is composed of a transmembrane protein called opsin and a light-sensitive molecule called 11-cis retinal. Each different pigment is especially sensitive to a certain wavelength of light (that is, the pigment is most likely to produce a cellular response when it is hit by a photon with the specific wavelength to which that pigment is most sensitive). The three types of cones are L, M, and S, which have pigments that respond best to light of long (especially 560 nm), medium (530 nm), and short (420 nm) wavelengths respectively.
   If the spectrum is wrapped to form a color wheel, magenta (additive secondary) appears midway between red and violet. Violet and red, the two components of magenta, are at opposite ends of the visible spectrum and have very different wavelengths. The additive secondary color magenta, as noted above, is made by combining violet and red light at equal intensity; it is not present in the spectrum itself.
  
  Section::::Fuchsia and magenta.
  
presuppositions: Highest and lowest frequency colors would clash on a color spectrum. The color spectrum cannot be wrapped into a continuous color wheel since the highest and lowest frequency colors would clash.
corrections: Red, blue, and green are the only colors of light our eyes detect and our minds blend them smoothly to perceive varying shades of colors which are unable to clash..  Our mind can blend the colors smoothly.
raw_presuppositions: Highest and lowest frequency colors would clash on a color spectrum. The color spectrum cannot be wrapped into a continuous color wheel since the highest and lowest frequency colors would clash. The color spectrum cannot be wrapped into a continuous color wheel since the highest and lowest frequency colors would clash.
raw_corrections: Red, blue, and green are the only colors of light our eyes detect and our minds blend them smoothly to perceive varying shades of colors which are unable to clash..  Our mind can blend the colors smoothly. Our mind can blend the colors smoothly.