I'm a little confused about the approach to the frequencies here. Most light that we see (apart from laser light or the result of separating or filtering light with optical equipment) is not pure monochromatic light at a single frequency. This is clearly true for many colors in this chart which are given as combinations of additive primary colors. So, it is misleading to say that these colors have a single frequency or wavelength. Is the frequency given in the chart just the pure color that would be closest to the indicated color in some color space metric?
@schoen You do make some very good points, the wave lengths in this list are based on the assumption of pure colour forms using Dan Bruton's Spectra approximation. http://www.physics.sfasu.edu/astro/color.html
Furthermore as you can see in the list composite colours such as white, gray and black have undefined values.
"<...> pure colour forms using Dan Bruton's Spectra approximation<...>"
Approximation or not, you cannot assign a unique wavelength or frequency to perceptual (extra-spectral) colors if for no other reason than that the given λ(f) is factually incorrect. Moreover, even an approximation doesn't make much sense, as simply human vision perceives magenta as a very different color to say various shades of pink (white + red) or any other color near red [orange. orange-red, etc.]. Basically, there is no single λ(f) - spectral - color that looks even vaguely like magenta (similarly for cyan, 'fuchsia' etc.).
This chart is misleading in that it intersperses both true spectral colors (red, yellow, blue etc. that actually possess unique wavelengths) with extra-spectral colors such as magenta, cyan, etc. which, per se, DO NOT have unique wavelengths/frequencies—but which this diagram incorrectly assigns to them.
Non-spectral/extra-spectral colors (magenta etc.) do not exist as true colors on the visible spectrum as such, rather they are 'perceptual' in that they are created in our minds by mixtures of other colors (e.g.: magenta being a mixture of red+blue).
A better understanding of how extra-spectral colors fit into the overall color schema and the way we perceive color can be gained from the 'CIE 1931 color space' (Chromaticity diagram).
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[ 3.3 ms ] story [ 23.5 ms ] threadFurthermore as you can see in the list composite colours such as white, gray and black have undefined values.
Approximation or not, you cannot assign a unique wavelength or frequency to perceptual (extra-spectral) colors if for no other reason than that the given λ(f) is factually incorrect. Moreover, even an approximation doesn't make much sense, as simply human vision perceives magenta as a very different color to say various shades of pink (white + red) or any other color near red [orange. orange-red, etc.]. Basically, there is no single λ(f) - spectral - color that looks even vaguely like magenta (similarly for cyan, 'fuchsia' etc.).
Non-spectral/extra-spectral colors (magenta etc.) do not exist as true colors on the visible spectrum as such, rather they are 'perceptual' in that they are created in our minds by mixtures of other colors (e.g.: magenta being a mixture of red+blue).
Why extra-spectral colors exist is a rather complex matter and stems from the very specific way we humans perceive colour (Young-Helmholtz tri-color perception theory https://en.wikipedia.org/wiki/Young%E2%80%93Helmholtz_theory)
A better understanding of how extra-spectral colors fit into the overall color schema and the way we perceive color can be gained from the 'CIE 1931 color space' (Chromaticity diagram).
https://en.wikipedia.org/wiki/CIE_1931_color_space.