Abstract: A gradation level selecting circuit for selecting a gradation level consists of first and second selecting circuits (28, 29) and a selector (30). The first selecting circuit selects one of gradation level signals from a gradation level generator in accordance with monochrome data from a monochrome data generator (24) and predetermined one of color data from a color data generator (23). The second selecting circuit selects one of the gradation level signals in accordance with the color data. The selector (30) selects an output of the first selecting circuit (28) or an output of the second selecting circuit (29) in response to a content of a switching resistor (25), to supply it to a monochrome display device. Thus, appropriate gradation display can be carried out by the monochrome display device using software either for color display or for monochrome display.