A method and an apparatus for correcting video signals are provided for printing simulation with a color monitor. Excellent mixed-color simulation can be performed in a printing process processing with a relatively high U.C.R.%. Mixed-color signals of secondary colors, a tertiary color, a quaternary color, black x primary colors, and black x secondary colors are detected from the signals (Y), (M), (C) and (K) for yellow Y, magenta M, cyan C and black K. The mixed-color signals are subjected to overlap compensation to provide overlap-compensated mixed-color signals. The signals (Y), (M), (C) and (K) are corrected using the overlap-compensated mixed-color signals so as to reduce color value of the mixed-colors in small portions. Printing simulation with a color monitor is facilitated. A correction/conversion method and an apparatus therefor are also provided which have a function of mixed-color correction and a function of converting the signals (Y), (M), (C) and (K) into signals (B), (G) and (R) for the color monitor.