October 2020
Volume 20, Issue 11
Open Access
Vision Sciences Society Annual Meeting Abstract  |   October 2020
Are there four, six, or seven unique hues?
Author Affiliations
  • Christopher Tyler
    Smith-Kettlewell Eye Research Institute
Journal of Vision October 2020, Vol.20, 273. doi:https://doi.org/10.1167/jov.20.11.273
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      Christopher Tyler; Are there four, six, or seven unique hues?. Journal of Vision 2020;20(11):273. doi: https://doi.org/10.1167/jov.20.11.273.

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      © ARVO (1962-2015); The Authors (2016-present)

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Rationale. Newton originally identified seven distinct hues in the rainbow, whereas the predominant choice of current color theory is four unique hues, following the four poles of Hering’s Opponent Color Theory. This coding is brought into question by the complementary colors of the CMYK system and of color afterimages, in which each corner of the triangular red/green/blue (R/G/B) color space has a distinct complementary color (cyan, magenta and yellow, respectively), supported by a reanalysis of color opponency in neurophysiological data (Pridmore, 2013). This sextet of unique hues is further supported by a new demonstration of luminance compression of the cone signal modulation in the color circle, to equalize the two interleaved trios and provide six dominant colors. Methods. To assess afterimage colors, test patches of 45 cd/m2 spanning the color gamut (R, G, B, R+G, G+B, and B+R) were viewed on an equiluminant background for 10 s to the left of fixation and replaced with an outlined blank comparison patch to the right in repeated 2 s cycles, whose color was adjusted in hue, saturation or intensity relative to match the afterimage at left. Results. Strongly saturated afterimages were obtained. To a tight specification, the afterimage CIE coordinate lines intersected at the chromaticity neutral point, highly distinct from the yellow balance point for the red/green opponent system. Afterimages thus conform to a complementary, rather than opponent, color organization consistent with each of the three primary colors (red, green and blue) having a distinct complementary counterpart (cyan, magenta and yellow, respectively), and vice versa. Conclusions. These results suggest that human color perception should best be characterized by six unique hues corresponding to the complementary pairings, rather than the four unique hues implied by the Hering opponent processes, which are not accurately supported by many forms of data.


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