Dose the blackened lubrication oil needs to be replaced for flying safety? Since there is very limited room for inaccurate assessment of oil quality due to strict flying safety standards, much aviation lubrication oil is disposed in advance long before their service life. More important, aircrafts still face the fatal challenges from unpredictable lubrication oil deterioration. Color change is surely a significant signal to diagnose the quality of lubrication oils. Based on the colorimeter, the color numbers of the testing lubrication oils are measured in this paper to identify the color variation degree of the oxidized lubrication oils. Then the molecular structures of the oxidized lubrication oils are investigated to find the intrinsic relationship between the oxidation products and color numbers. Based on key performances of the oxidized oil samples, the oil quality is undoubtfully deteriorated which is coincident with the variation of color number. The color numbers of the used aviation lubrication oils could provide an alternative way to readily and quickly measure the decline degree and residual lifetime.