The feasibility of a virtual colored overlay is based on constraints of computer and user preference and it is evaluated for people with Scotopic Sensitivity Syndrome. We draw and chromaticities of virtual colored overlay which will be implemented on IT devices by measuring optical characteristics of 2 representative film overlays and simulating them. We analyzed the influence of two illuminating conditions on the virtual colored overlay. We find that it is possible to get the multiple combinations of alpha and source RGB values to match a chromaticity which is presented in CIE-Luv color space under ideal white condition of display, a user can select one among them with respect to clarity and comfort. Under 100 lx difference of illumination conditions, the changes of chromaticities are negligible, but luminances are increased 37.8 cd/㎡ average(std 2.006) at high illumination condition.키워드 : 필름 오버레이, 광과민성 증후군, 컴퓨터화된 색 오버레이, 주변조명, 포화도