PENCIL COLORS

        There are 24 colors available for PENS. Colors 0 and 7 are  SPECIAL,
    colors  1 to 6 are FIXED (named colors or their equivalent shade of grey
    on grayscale terminals). The last 16 are user-defined.

    Color 0 (the default for the default PEN 0)  is  ALWAYS  the  foreground
    color (i.e., always visible whatever the background color of the graphic
    window is), and becomes BLACK on the paper hardcopy. Color 7  is  ALWAYS
    the background color, useful for text written on an grey-scale image for
    example.

    Colors 1 to 6 are  defined  as  follows  for  a  standard  display  with
    sufficient colors available in its colormap:
        "red","green","blue","cyan","yellow" and "magenta"
    For grey-scale displays, it becomes:
        "grey42","grey70","grey14","grey28","grey56" and "grey84"
    This may vary depending on  the  number  of  available  colors  on  your
    display.

    The last 16 colors are user-definable (see HELP LUT) and  correspond  to
    the  16  'FILL  PENS'  used  as  fill  colors  in various commands, like
    RGM/GREY or POLYGON/FILL.