The visual data, obtained from the just-noticeable color difference discrimination threshold experiment carried out in CIELAB color space, were used to test the four classical color-difference formulae, CIELAB, CMC,CIE94 and CIEDE2000. The just-noticeable color difference discrimination thresholds of the printed samples’ different color regions calculated by different formulae are different. Except for the grey color region,the CIELAB color-difference is higher than others. For the original forms (kL=kC=kH=1), CIEDE2000 ouerforms others with the best matching with visual evaluation. For the color-difference formulae with optimized kC and kH, the optimized form of CIEDE2000 performs the best especially in the color region of grey and high chroma orange.