The experiments in this study evaluated three independent variables: lighting color, illumination intensity, and text color. Two levels of lighting color were tested, white light used for general offices and yellow light for the etching process in photo area of semi-conductor factories. Three levels of illumination intensity were tested: 250 lux (low-level office illumination), 500 lux (normal office illumination), and 1000 lux (high-level office illumination). Four text colors were employed, including the three primary colors (red, green and blue) and a center-point one (gray) in the CIE chromaticity coordinates. The four colors used were selected according to the criteria that their maximum luminance would be at least 40 cd/m2 and the set of colors should be distributed evenly and widely in the chromaticity space. Table 1 show the CIE coordinates (L, x, y) of the text and background colors.