One object of an embodiment of the present invention is to provide a drive control circuit for a display device which is capable of displaying high-quality color images suited for external environment, display contents or the like by fully utilizing high representational capability of a display panel of multi-primary color configuration. A liquid-crystal color-display device includes a conversion circuit for adjusting a level of primary-color signals which represent the color images to be displayed. The conversion circuit receives four primary-color signals R1, G1, B1, W1 corresponding to four primary colors of red, green, blue and white as data signal for the color image display; then adjusts the level of these primary-color signals R1, G1, B1, W1 based on an externally inputted primary-color control signal; and outputs primary-color signals R2, G2, B2, W2 which are signals obtained by the adjustment. In the primary-color signal level adjustment process for the four primary colors based on the primary-color control signal, the adjustment is performed in such a way that a relationship between the inputted primary-color signal and the adjusted primary-color signal for a white color among the four primary colors is different from a relationship between the inputted primary-color signal and the adjusted primary-color signal for each of red, green and blue colors.