Colors on Multiple Display Monitors
Each monitor can have its own color depth. The system automatically adjusts colors as windows move across monitors with different color depths. In general, this produces good results. However, this is not always optimal. To take advantage of the color capabilities of different monitors, see the Painting on Multiple Display Monitors section that follows.
To determine if all monitors have the same color format, call GetSystemMetrics with SM_SAMEDISPLAYFORMAT.
If the primary monitor is palettized, SelectPalette and RealizePalette work the same as before, but across all monitors. In addition, the palettes of all palettized devices are synchronized. If the primary monitor is not palettized, SelectPalette and RealizePalette will select the palette into the background and palettized devices will not be synchronized.