PURPOSE: To enable smooth output of document data to a two color printing output device without requiring rewrite, at the time of outputting the document data formed in a single black color from a red and black two color output device, by providing a means for modifying the color of a random character data into red during printing stage.

CONSTITUTION: An output means 13c transfers character data in a document data eddited in a composing means 13a to a display control section 3. A character generator (CG) 14 generates a dot pattern of a character based on a character code fed from the output means 13c. The dot pattern is transferred to VRAM2 or a printer 10 so as to be displayed or printed. An output device judges whether said data are for two color printing of red and black of for a single color printing of black at the stage when a document file is transferred to the output means 13c. If said data are for a single color printing, they are fed straight to the display control section 3 then outputted. It said data are for two color printing, it is specified that which of big headline or sub-headline must be printed in red.