Color categories in color anomalous trichromats and dichromats

Observers with color vision deficiencies (CVD) tend to have similar color categories as trichromats, despite sometimes severe sensitivity limitations along the red-green. We investigated the similarity of color categories of anomalous trichromats and dichromats, compared to five color-normal trichromats. We also investigated whether EnChroma glasses could improve categorization for anomalous trichromats. Participants were asked to sort 450 Munsell chips (from the World Color Survey plus 40 desaturated chips) into 11 color categories. They then waited 2 hours wearing the glasses and sorted the chips again into the categories. They either did so with the glasses on while sorting the second time, or with the glasses removed after the adaptation phase. Five color-normal trichromats were measured for reference. We define 217 core chips as those where all trichromats agreed, and 444 majority chips as the ones where at least 3 out of the 5 agreed on the category. In line with previous findings, the color categories of the CVD observers matched the trichromats categories closer than compared to what simulations would predict. This was particularly the case for the core chips at the centre of the categories. Furthermore, for the anomalous trichromats, the color categories did not differ very much after wearing the EnChroma glasses for 2 hours, even when wearing the glasses during the second sorting task. The relatively high performance of the CVD observers may be due to the high saturation of most of the chips we used. It may also be supported by strategic sorting decisions, because the observers knew that the set of chips covered the whole color space.