Abstract: Color is added to the standard video display (18) of a computer numerical control system for controlling the operation of a machine tool (10) in the performance of specified operations with respect to a workpiece. Color assignment records (62) are included in the machine setup data (MSD) source file (54) for implementing background color, reverse video color, forms character color, data character color, errors and/or alarm color, operator required response color, and high-lite color. The MSD source file (54) is processed to generate a binary MSD file (56) which is then read into the numerical control basic (NC) software (24) which operates to generate both text and graphic displays. The original or default color assignments may be dynamically modified or changed through an MSD file editor (58).