Coloroid

[1] Like the OSA-UCS and Munsell systems, the Coloroid attempts to model a perceptually uniform color space or UCS.

The VAT components are used to define a cylindrical color geometry, with V as the achromatic vertical axis (lightness or brightness), T as the horizontal distance from the achromatic axis (chroma), and A as the hue angle around the hue circle.

The circumferential limits of this cylinder are defined by the spectrum locus, or colors as they appear in a single wavelength of light (or a mixture of single "violet" and "red" wavelengths); this ambit varies vertically in V around the hue circle, showing whether the relative luminance or brightness of each wavelength is high (yellow hue) or low (violet blue hue).

The Coloroid technical documentation defines the conceptual equations necessary to transform the Coloroid perceptual components VAT into the corresponding stimulus components, using the CIE XYZ 1931 color-matching functions with the D65 CIE illuminant.

However, a Coloroid Colour Atlas[4] is available that provides color exemplars at 16 levels of lightness out to as many as 13 increments in saturation for each of the 48 hue planes.

The Coloroid color space, showing the cylindrical geometry of luminosity (V), hue (A) and saturation (T), the relative components of pure hue (p), white (w) and black (s) that can be used to mix any hue within a single hue plane, and the relative areas of all possible (spectrally defined) colors and material (pigmented surfaces) colors according to Coloroid.