The traditional means for specifying color appearance, such as tristimulus colorimetry and matching to standard samples, have drawbacks in many applied settings: they need precise equipment, standardized viewing conditions, and may not work well with many self-luminous sources. Furthermore, the results often tell only about a match and not about appearance.
We have a technique for specifying color appearance that is reliable, very rapid, and can be used in any situation, since it requires no additional apparatus: subjects look at a stimulus and then simply state the proportions of their sensations using the four unique hue names, red, yellow, green, and blue; for completeness, they also state the apparent saturation. We have shown that the results are not biased by methodological factors including context and range effects, subjects’ linguistic backgrounds, and amount of practice. The procedure can be repeated quickly whenever viewing conditions change.
For analysis, the scaled sensory values elicited by a set of stimuli are used to derive the locations of the stimuli on a color diagram that is based on appearance and that has a uniform metric; we term this a Uniform Appearance Diagram (UAD). the orthogonal axes of this space are red-green and yellow-blue; the location of a stimulus specifies its hue and its distance from the origin specifies its apparent saturation.
It would be very useful if the results of our methods could be related to those from other specification systems. We argue that we can do so by deriving "traditional” measures of discriminability from our UADs. For example, we find that distances among stimuli on a UAD can be used to predict wavelength discrimination under the given viewing conditions.