1. An image generating device comprising: a background image acquirer configured to acquire an image of a background on which an image of an object is to be superimposed; a color extractor configured to extract a color about one or a plurality of places in the image of the background; a light source decider configured to decide a color of light output by a light source that illuminates the object based on the color extracted about the one or plurality of places; a drawing section configured to draw the image of the object based on the decided color of the light of the light source; and an output image generator configured to generate an output image obtained by superimposing the image of the object on the image of the background.