@RGBCOMPL — Returns a complementary color.

Syntax:
%@RGBCOMPL[color,rotate]

colormay be specified as #rrggbb or as a W3C color name.
rotatedegrees to rotate the color’s hue; defaults to 180

If you specify the color in hexadecimal with a leading # sign, it must be either three or six hex digits long. If it’s three digits long, each digit is doubled; #8ac is the same as #88aacc. Alternatively, you can use a leading 0x and the rules above do not apply; the number of digits is not significant.

The input color is plotted on a color wheel, and the color opposite (180° around, or according to rotate) is returned. The resulting color is returned as a six-digit hexadecimal value, #rrggbb; for example, #5b6d85. It can be used as the color argument to the BGCOLOR command.

rem  Set the background color to contrast with the wallpaper:
if "%_wallpaper" ne "*none*" bgcolor %@rgbcompl[%@imgcolor["%_wallpaper"]]


See also: the BGCOLOR command, which sets the background color; the _BGCOLOR variable, which returns the current background color; and the @IMGCOLOR function, which returns a color from a graphics file.