Threshold and suprathreshold perceptual color differences

Observers matched a series of colors. They also matched a given neutral difference by producing, with a colorimeter, a color difference for one color attribute at a time (producing a saturation difference while keeping hue and lightness constant, producing a hue difference while keeping lightness and saturation constant, and producing a lightness difference while keeping hue and saturation constant). We found it possible for observers trained in color scaling to abstract the individual color attributes of hue, saturation, and lightness; that a unit suprathreshold perceptual color ellipsoid can be described about a given color in color space; that the precision of color-difference matching seems to be a function of the size of the perceptual color interval of the reference colors; and, finally, that there is a tendency for color-difference-matching ellipses to orient toward the nearest colorimeter primary.