Fig. 1. Diagram of chromaticity coordinates in color constancy index calculation

Fig. 2. Diagram of experimental scene

Fig. 3. CIE 1976 u'v' chromaticity coordinates of the neutral and four chromatic illuminants

Fig. 4. Relative spectral power distributions of the neutral and four chromatic illuminants produced by the RGB-LED light source

Fig. 5. Response frequency of each color category. (a) Average data of 7 subjects in experiments which use red and green illuminants; (b) average data of 5 subjects in experiments which use blue and yellow illuminants.Error bars represent standard error of mean. G: green, B: blue, R: red, BR: brown, P: purple, GY: gray. PK: pink, O: orange, Y: yellow

Fig. 6. Comparison of the classification results under neutral illuminant and four chromatic illuminants for one subject. (a) Red illuminant; (b) green illuminant; (c) blue illuminant; (d) yellow illuminant. Category name plus N denotes color category under the neutral illuminant

Fig. 7. Color constancy index. (a) Constancy index of each color category under four chromatic illuminants; (b) overall indices under four chromatic illuminants. Data in Fig. 7(a) and Fig. 7(b) are average values of subjects. Error bars represent standard error of mean

Fig. 8. Angular deviation. (a) Angular deviation for each color category under four chromatic illuminants; (b) overall angular deviations under four chromatic illuminants. Data in Fig. 8(a) and Fig. 8(b) are average values of subjects. Error bars represent standard error of mean

Fig. 9. Average color difference between simulated spectra and the value under neutral illuminant in this study over 240 Munsell surfaces when the peak wavelengths of blue, green, and red LEDs are different. (a) Blue LED; (b) green LED; (c) red LED. Error bars represent standard deviations