The BitsPerPel property indicates the number of bits used to represent the color in this configuration (the bits per pixel). ...

The BitsPerPel property indicates the number of bits used to represent the color in this configuration (the bits per pixel).
Example: 8.  
This property has been deprecated in favor of a corresponding property(s) contained in the Win32_VideoController, Win32_DesktopMonitor and//or CIM_VideoControllerResolution