The following is a summary of “Invariant categorical color regions across illuminant change coincide with focal colors,” published in the February 2023 issue of Ophthalmology by Morimoto, et al.

Do certain areas of a color space exhibit color categories that are unaffected by illuminant changes? If true, what qualities distinguish them from other regions as being more stable? To answer these inquiries, researchers asked participants to identify the hue of 424 colored surfaces displayed one at a time under varied chromatic illuminants. 

Findings revealed a high level of categorical color constancy, particularly when illuminated by natural light sources. Also, surfaces chosen as a focal color—the greatest illustration of a color category—were more resilient to illuminant alteration than nonfocal color samples. Also, using surfaces that were all designated gray, they conducted an asymmetric color-matching experiment to measure the shift in color appearance brought on by illuminant changes. 

This allowed them to separate the appearance-based color constancy from the categorical color constancy (which was often confounded). Despite the fact that all of the samples were given the color gray, the results indicated that color samples’ appearances changed significantly as a result of illuminant variations, demonstrating that a color category’s constancy was much more resilient than its appearance constancy.