An on-screen signal processing apparatus comprises a first display memory for storing binary image data, a second display memory for storing decoration data (i.e., “attribute data”) for decorating the binary image data stored in the first display memory in a unit of a fixed plurality of pixels, and a first color look-up table for storing data concerning a character color and a background color for decorating the binary image data stored in the first display memory. A first converter reads the binary image data of the first display memory and the decoration data of the second display memory every unit of the fixed plurality of pixels and searches the first color look-up table based on the character color and the background color designated in the decoration data, and further performs color-conversion to the binary image data of the first display memory.