Denoting a maximum value of three primary color signals RGB by Max, a minimum value by Min, and coefficients by a and b, the color temperature of only colors close to achromatic colors is changed by adding (a*Min-b*Max) to the signal B. Denoting a luminance level by Y, and coefficients by c and d, the color temperature of only colors close to achromatic colors is changed by adding (c*Y-d*(Max-Min)) to the signal B. Color temperature of only colors close to achromatic colors is changed by multiplying the signal B by a coefficient based on a value of (Man-Min)/Max, which represents saturation.