alloc_color/[2,3,4,5]
alloc_color(+Color, -Pixel) alloc_color(+Colormapable, +Color, -Pixel) alloc_color(+Colormapable, +Color, -Pixel, -Actual_color) alloc_color(+Colormapable, +Color, -Pixel, -Actual_color, -Exact_color)
Pixel is a (possibly newly allocated) pixel value for the colormap
associated with Colormapable that
is as close as possible to Color. Color is a color spec, as
described in pxl-col-cs.
Actual_color is the actual color of Pixel in Colormapable,
and Exact_color is the color that should have been allocated (the same as
Color, if it is a color/3
term). Colormapable defaults to
the default
screen (which means the color is allocated in the default screen's
default colormap).