Abstract: On the basis of the colorimetry and Photoshop image software, the appraisal for the colours of ruby samples is studied by a quantitative method in the paper.The photographs of samples from light red to dark red and standard colours of ruby samples in GemSet are input into the computer by using a digital camera or UMAX scanner,which are analysed through the parameter values of hue (H), saturation (S) and brightness (B) in Photoshop software. The values are used to grade colour, saturaion, brightness and an integrative criterion for quantitative appraisal of colour of ruby is established. The results show that the method is feasible and practical.