Specifies the foreground color to use when drawing the components of this element,
such as the content for token elements or any lines, surds, or other decorations.
It also establishes the default mathcolor used for child elements
when used on a layout element.
Specifies the background color to be used to fill in the bounding box
of the element and its children. The default, "transparent", lets the
background color, if any, used in the current rendering context to show through.