What is the term for the imaginary colors that appear at each Copunctal point in the CIE diagram?

The term "imaginary colors" specifically refers to the colors that can be found at the copunctal points in the CIE (Commission Internationale de l'Éclairage) color space diagram. These points represent areas in the color space where there are no actual wavelengths of light that correspond to those colors, hence they cannot be produced by any real light source.

Imaginary colors arise due to the limitations of the physical spectrum of light and the perception system of humans. In the context of colorimetry, imaginary colors help to understand and represent the relationships between different colors and their saturation or tonal qualities without being constrained by the wavelengths of visible light.

In contrast, real colors, chromatic colors, and saturated colors are terms used to describe actual, perceivable colors that exist in the physical world, based on the wavelengths of light that can be detected by the human eye. Therefore, "imaginary colors" stands out as the correct term for the hypothetical colors represented in this specific area of the CIE diagram.