Color appearance: properties of the uniform appearance diagram derived from hue and saturation scaling.

Color appearance can be specified by a procedure of direct hue and saturation scaling. The scaling data can be represented on a 2-D color space termed a uniform appearance diagram (UAD). The orthogonal and bipolar axes of the UAD are based on the four unique hue sensations, which are blue-yellow and green-red. We have previously shown that the technique is reliable and rapid. We now show that the UAD is sufficiently uniform metrically that it can be used to derive, from a single set of scaling data, a wide range of color functions, such as the spectral loci of the unique hues, wavelength discrimination, and similarities among very different colored stimuli. The advantage of deriving a UAD is that it requires only a modest amount of participant time to generate the relevant data, which can be re-generated quickly to meet changing viewing conditions.