Using the same color in PyX and in LaTeX

! This example shows three different methods how to use a color defined in PyX
also in LaTeX.... In the example code, we first define a cmyk color `col`,
which is then used to define a color `COL` in LaTeX. The latter is then used in
a LaTeX expression.

! The same behavior can be achieved by two different methods in `c.text`,

    r"\textcolor[named]{PineGreen}{Text} and outline ..."
    r"\textcolor[pyx]{color.cmyk.PineGreen}{Text} and outline ..."

They are not as elegant as the above shown, since we need to insert the color
definition `PineGreen` explicitly. The first alternative makes use of the
`named` color model of color.sty. All colors of this model are predefined also
in PyX. The other alternative allows to use PyX colors directly.

!! Note that no graphics driver has been used for the color.sty LaTeX package.
PyX performs a hack to enforce the use of its own LaTeX driver file pyx.def. In
case that you have installed the three files `pyx.def`, `color.cfg`, and
`graphics.cfg` from the PyX distribution somewhere in the LaTeX search path, it is
possible to use

    text.set(mode="latex", pyxgraphics=0)
    text.preamble(r"\usepackage[pyx]{color}")

which is the more aesthetic variant.