Library /sys$common/syshlp/examples/decw/custom.hlb Overview, multihead  *Conan The Librarian (sorry for the slow response - running on an old VAX)

               The color customizer only affects applications started on
               the same screen as the customizer. On multihead systems,
               you can start a different color customizer for each screen
               and have a different palette in effect on each screen.

               The color customizer can be configured so that it is
               invoked once and affects all applications regardless of
               where they are started. This mode can be turned on by
               modifying the Custom.multiScreen resource in the CUSTOM.DAT
               defaults file as follows:

               Custom.multiScreen: True

               The default value is False.