The following questions were raised to chroma and hue scales of the nonlinear color-appearance model: 1) significant nonuniformities of the chroma scales for different hues, and 2) deviations of hue scale between the model and the Munsell and the NCS schemes. It was suggested that the problems were ca used by the use of the coefficient e(s)(theta) proposed by Hunt. Instead of e(s)(theta), a new coefficient E(S)(theta) was proposed, which corresponds to the chromatic strengths of spectral colors (including colors on the red-purple locus). By using E(S)(theta), the nonlinear color-appearance model could predict the hue and chroma scales of the Munsell and the NCS schemes quite nicely. The method in the present study is generally applicable for determining hue and chroma perceptions of object colors irrespective of the color-appearance model used.