Why Did Newton See Indigo in the Spectrum?

Abstract

The arrangement of colors in Newton's color circle suggests that it was derived from paint mixtures, not light mixtures. If this is true, we are led to conclude that what Newton called indigo represents violet in modern terminology, and what he called violet represents purple. The author hypothesizes that Newton saw seven reasonably distinct colors in the artist's paint mixture color circle (red, orange, yellow, green, blue, violet, and purple) and therefore assumed he could also see seven distinct colors in his crude spectral projections.

Are there nontrivial constraints on colour categorization?

“…This is also the hue family of the Munsell system. However Biernson (1972) claims that orange must be added, and Campbell (1983) doubts whether yellow can be seen between green and red (see also Duck 1987 andKidder 1989). As to the colours of the rainbow Gage (1993, p. 93) suggests "the very delicacy of the transitions of the bow .…”