A psychophysical experiment was carried out with the method of constant stimuli using CRT-generated color samples. The experimental results at the five CIE color centers of Gray, Red, Yellow, Green, and Blue were satisfactorily described by chromaticity ellipses as equal color-difference contours in the CIELAB space. The CIEDE2000 formula, together with other two advanced color-difference formulae, CMC and CIE94, and the basic CIELAB equation, were tested using the visual data obtained from the present experiment. The comparisons between color differences, ΔE, predicted by individual formulae and the corresponding visual scales, ΔV, were carried out in terms of PF/3 measure. With their original forms, i.e. kL=kC=kH=1, or with their optimized kL values, the CIEDE2000 outperformed others for the combined dataset under the viewing condition in this study. Furthermore, the visual data at Blue center were well predicted by CIEDE2000 with an obviously better accuracy than other color-difference formulae. This confirms that the rotation item involved in the CIEDE2000 equation effectively improves the uniformity and predicting performance for the color differences in the blue region.