Imaged-based maps record variety of spatial information which can be treated as the role that traditional maps play. For the complex digital background, symbols' color design must be modified to keep traditional map's color characteristics, to achieve the best visual contrast around their surroundings, and to show the figured-ground phenomenon in the screen. Two experiments were involved in this study to check the tourist map function: First, selecting the best symbol color among red, orange and yellow lights. Second, examining color function with different symbol shapes. The conclusions reflect that symbols with yellow light (L=80_ will generate the best legibility in the image-based maps, the result also approve that shape will not affect the color function significantly.