The term "foreground color" is misleading.
Here, "foreground" means the top layer of a cell's background.
To set the color of a cell's contents, use the
setColor() method.
mixed $color -
either a string (like 'blue'), or an integer (range is [8...63]).
See the "Using colors" section,
below, for more information.
Using colors
The following colors can be defined by name:
black, white,
red, green,
blue, yellow,
magenta and cyan.
To learn what the other indexed colors look like, read
Color Palette and the 56 Excel
ColorIndex Colors.
Beware that the color indexes listed there are displaced by 1
with respect to those used by
Spreadsheet_Excel_Writer.
If the predifined colors don't meet your requirements,
use the setCustomColor() method.