[pstricks] Transparent color

[Rafael Castro Triguero]

Hello PSTricks users,

I would like to know why I get this error when I am trying to use 
\psset{fillstyle=transparent,linestyle=none} like in the example of 
Pstricks web site

Undefined fillstyle: 'transparent'

My example is

\begin{figure}[h]
\centering \psset{yunit=0.5,fillstyle=transparent}
\begin{pspicture}(-2,0)(2,9)
\pspolygon[fillcolor=blue](-3,0)(-3,7)(3,7)(3,0) 
\pspolygon[fillcolor=brown](-3,7)(-3,9)(3,9)(3,7)
\psline[linewidth=2pt](-4,0)(4,0) \psline(-3,4)(3,4) 
\psline[linewidth=0.5pt](-3,7)(3,7) \psline(-3,9)(3,9)
\psline(-3,0)(-3,9) \psline(3,0)(3,9)
\end{pspicture}
\end{figure}

Lot of thanks

--
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PhD. Student Rafael Castro Triguero
University of Córdoba
Polithecnical School
Menéndez Pidal Avenue
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Spain

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