The effect of the proportion of blue on a plate, between white and blue, on the appetite was investigated. Three types of plate were used: Japanese, Western, and Chinese style plates that were blue and white, or only blue. Depending on the ratio of blue to white, the plates were classified into four groups: A (10-20%), B (25-35%), C (55-65%), and D (100%). Two meals of Japanese, Western, and Chinese food, involving a total of six dishes, were served on each type of plate, and photographed. An evaluation panel looked at the pictures of the A, B, C, and D plates simultaneously and evaluated their effect on appetite by scoring on a questionnaire. The evaluated mean value for the A plates was significantly higher than that for C and D, suggesting that the plates with a blue-to-white ratio of 10-20% increased the appetite. The evaluated mean appetite value for D was significantly low with all the meals, suggesting that all-blue plates reduced the appetite. The correlation coefficient between the ratio of blue to white and mean appetite was -0.79, indicative of a negative correlation between these variables. The effect of the saturation of blue was also examined. Plate E with a blue-to-white ratio of 100% at a lower saturation than D was tested, and a similar questionnaire survey was conducted. The evaluated mean appetite for E was lower than that for D in all cases except with one Western meal. The results suggest that a blue plate with low saturation reduced the appetite more than a blue plate with high saturation.