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Specific incidental colors can be requested through the setfg
(for the foreground color) and setbg (background color) commands
and their aliases. The foreground color is used also for line drawings
(e.g., plot) and calligraphy (e.g., callig). The color can
be identified in two ways: through a color name, or through a set of
three numbers.
SETFG,'color-name' sets the foreground color to that specified by
the color-name – if that name is recognized. Color names can be
either proper names (such as blue or black) or various
kinds of color space coordinate "names". In general, colors can be
identified by three independent numbers, and there are many different
color coordinate systems in use. You specify a color string in a
particular recognized color coordinate system by constructing a name
that consists of the color coordinate system (case-insensitive) name
followed by a colon : followed by the three corresponding
coordinates separated by forward slashes /.
The following two color coordinate systems specify colors in a device-dependent manner:
'rgb:<red>/<green>/<blue>' with <red>,
<green>, and <blue> three integer numbers consisting of up
to four hexadecimal digits (case insensitive). The number FFFF
indicates maximum intensity in that color, and 0000 indicates
total absence of that color. If fewer than four hexadecimal digits are
specified, then hexadecimal zeros are affixed. In other words, the
following two specifications are equivalent: 'rgb:ff/002/3a' and
'rgb:ff00/0020/3a00'.
'rgbi:<red>/<green>/<blue>' is similar to
'rgb:<red>/<green>/<blue>' except that the numbers are now
floating point and between 0.0 and 1.0 (with an optional sign and
an optional exponent introduced by e or e).
The following six color coordinate systems specify colors in a device-independent manner:
'CIEXYZ:<X>/<Y>/<Z>'
'CIEuvY:<u>/<v>/<Y>'
'CIExyY:<x>/<y>/<Y>'
'CIELab:<L>/<a>/<b>'
'CIELuv:<L>/<u>/<v>'
'TekHVC:<H>/<V>/<C>'
The numbers in all of these specifications are floating point, with optional sign and exponent.
SETFG,[r,g,b] sets the foreground color to the color defined by
the RGBI values r (for red), g (for green), and b
(for blue). All three numbers should be floating-point between 0.0
(absent) and 1.0 (maximum). The specification SETFG,[r,g,b]
corresponds to SETFG,'rgbi:r/g/b'.
See also: setfg, setbg, plot, callig
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