If this option is not set, the available X Server display colors are mapped to the colors needed by DOS or Windows, but the mapping may not be exact.
One side effect of selecting Use Private Colormap is that every time you switch between a Linux window and the Win4Lin window, your whole screen flashes as the colormaps are switched. Also, if the colormaps are vastly different, you can only see the contents of the window that is currently active.
Click on OK to apply the changes to the current session.
Click on Cancel to dismiss the Options dialog box without making any changes.