Mobile displays such as PDAs and cellular phones can be placed under various illumination levels, different from the flat panel displays mainly used in the indoor environment. In particular, in the daylight condition, the displayed images or text on a mobile display can be darkly perceived, i.e., the degradation of sunlight-readability. In this paper, we consider why this kind of problem occurs in mobile phones and suggest the illumination level adaptive color reproduction method with lightness adaptation model and flare compensation.