PENCIL /COLOUR
Keywords: greg

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PENCIL /COLOUR

            PENCIL [N] /COLOUR Arg

        Modify the current pen color, or the color of the N-th pen.

        The argument can be a color name (subset of  the  X11  colors  catalog),
        e.g. RED, LIGHT_SEA_GREEN, MEDIUM_BLUE... The complete list is available
        by typing "PENCIL /COLOUR ?". The colors can also be displayed thanks to
        the  demonstration  procedure "@ gag_demo:demo-pencolors.greg". The list
        is also available in the character array GTV%COLORS for  use  in  proce-
        dures.

        There are 3 special color names:
          BACKGROUND  resolves  as WHITE on white devices and BLACK on black de-
                     vices,
          FOREGROUND resolves as BLACK on white devices and WHITE on  black  de-
                     vices,
          NEGATIVE  inverts  the  pixel colors below the graphical segment begin
                     drawn. This ensures that the  segment  is  always  visible,
                     whatever  the context. NEGATIVE is supported only for X and
                     PNG devices. Other devices use the FOREGROUND  color  as  a
                     fallback.

        The argument can also be an integer value (explicit, or a variable name,
        or the result of a math expression) from -1 to  23  with  the  following
        signification:
          -1 NEGATIVE
           0 FOREGROUND
           1 RED
           2 GREEN
           3 BLUE
           4 CYAN
           5 YELLOW
           6 MAGENTA
           7 BACKGROUND
           8  to 23: those 16 colors can be customized by the user (see HELP LUT
             /PEN for details). They can be used as any other  color,  but  they
             also correspond as the "fill pens" used by the command RGMAP /GREY.
             Those colors are dynamic, i.e., by default, changing them will also
             modify  the  segments  previously  drawn with them (see HELP CHANGE
             LUT).