A high colour device is one that has more than 8 bits per pixel (i.e. more than
256 colours). A high colour device does not make use of colour palettes. If you
want to use a wide range of colours whilst avoiding the complexities of
managing a palette, one solution is to restrict the usage to desktops operating
in high colour mode. Thus you can use this function to test if the desktop is
set to operate with more than 256 colours per pixel and to send a error message
and close down on failure.