1. An image display device, comprising: a light-emitting unit; a display panel including color filters of a plurality of colors and pixels corresponding to the respective color filters; a sensor which detects light from the light-emitting unit and light incident from outside that passes through the display panel; an acquisition unit configured to acquire, in a state where the display panel is controlled so that, relative to transmittance of pixels of one color among the plurality of colors, transmittance of pixels of colors other than the one color becomes smaller, a detection value that is output from the sensor as a first detection value of the one color; and a determination unit configured to determine an irradiation condition of external light based on the first detection value of each color of the plurality of colors acquired by the acquisition unit.