A pre- and post-between groups experimental design with nine treatment groups was conducted to determine the effects of interior office colors on subject＇s clerical task performance, mood, and color preference. A total of 675 subjects participated in the study. The dependent variables were proofreading performance tasks, six mood states, and color preference. Independent variables were nine office colors, two saturation levels (high or low), two value levels (dark or light), warmth or coolness of the colors, and gender. The data were analyzed by using multivariate analyses of covariance and analyses of variance. The results showed that subjects made significantly more proofreading errors in the white office than in the blue and red offices. Females performed significantly better than males. Moreover, the saturation of the colors seemed to be a salient predictor of differences between females and males. Females indicated more depression, confusion, and anger in low-saturated office colors (white, gray, beige), whereas males reported more depression, confusion, and anger in the high-saturated office colors (green, blue, purple, red, yellow, and orange). Further, subjects revealed that they would be least likely to work in the beige and white offices. Implications for future research on the effects of colors on office worker performance and mood are discussed.