The advantages of the Commission Internationale de l'Eclairage (CIE) color measurements and the use of the standardizable purified azure B-eosin Y stain, as compared to the commonly used commercial Giemsa stain, were studied. Color measurement and analysis according to the CIE standards allows the comparison of color measurements from different slides stained by either the same or different procedures. Moreover, measurements from different cytophotometric systems can be compared. The results can also be directly correlated with human visual subjective color estimates and thus used to quantify the human observations. The color information in the air-dried cell specimens, which differs from the color characteristics of the components of the staining solution, was measured and analyzed.