\documentclass{article}
\usepackage{web}
\margins{0pt}{0pt}{0pt}{0pt}   %% Kein Seitenrand
\screensize{130mm}{150mm}      %% Dimensionen: H\"{o}he, Breite des Dokuments

\parindent0pt

\usepackage{pstricks,pstricks-add}

\definecolor{belgiumYellow}{RGB}{255 233 54}
\definecolor{belgiumRed}{RGB}{255 15 33}

\begin{document}

\thispagestyle{empty}

\begin{pspicture}(0,0)(15,13)
%% Flagge (Verh\"{a}ltnis 15 Breite : 13 H\"{o}he)
\psframe[linecolor=black,fillstyle=solid,fillcolor=black](0,0)(5,13)
\psframe[linecolor=belgiumYellow,fillstyle=solid,fillcolor=belgiumYellow](5,0)(10,13)
\psframe[linecolor=belgiumRed,fillstyle=solid,fillcolor=belgiumRed](10,0)(15,13)

\end{pspicture}
\end{document}
