Historical data of chroma scaling and hue scaling are compared and evidence is shown that we do not have a reliable basis in either case. Several data sets indicate explicitly or implicitly that the number of constant sized hue differences between unique hues as well as in the quadrants of the a*, b* diagram differs making what is commonly regarded as uniform color space inhomogeneous. This problem is also shown to affect the OSA-UCS space. A Euclidean uniform psychological or psychophysical color space appears to be impossible.
Rolf G. Kuehni,
"Uniform color space is not homogeneous", Proc. SPIE 4421, 9th Congress of the International Colour Association, (6 June 2002); doi: 10.1117/12.464529; https://doi.org/10.1117/12.464529