Past studies found that displays and surface colors needed very different chromaticities to produce white appearance and attributed such a difference to the different degrees of chromatic adaptation caused by the viewing media. This study aimed to test whether the different chromaticities for producing white appearance were caused by viewing medium or viewing mode. Observers were asked to adjust the stimuli at different luminance levels on an iPad display until they appeared white under different adapting conditions (i.e., adapting luminance and adapting chromaticities). The results clearly suggested that the different chromaticities for producing white appearance were due to the viewing mode of the stimulus, which was jointly affected by the stimulus luminance and adapting luminance, rather than viewing medium. It also suggested the necessity to develop a comprehensive color appearance model and uniform color space for self-luminous stimuli, which will be important to the color reproduction in HDR imaging systems.