\documentclass{article}
\usepackage{web}
\margins{0pt}{0pt}{0pt}{0pt}   %% Kein Seitenrand
\screensize{150mm}{250mm}      %% Dimensionen: H\"{o}he, Breite des Dokuments

\parindent0pt

\usepackage{pstricks,pstricks-add}

\definecolor{lithuaniaYellow}{RGB}{253 185 19}
\definecolor{lithuaniaGreen}{RGB}{0 106 68}
\definecolor{lithuaniaRed}{RGB}{193 39 45}


\begin{document}

\thispagestyle{empty}

\begin{pspicture}(0,0)(25,15)
%% Flagge (Verh\"{a}ltnis 5 Breite : 3 H\"{o}he)

\psframe[linecolor=lithuaniaYellow,fillstyle=solid,fillcolor=lithuaniaYellow](0,10)(25,15)
\psframe[linecolor=lithuaniaGreen,fillstyle=solid,fillcolor=lithuaniaGreen](0,5)(25,10)
\psframe[linecolor=lithuaniaRed,fillstyle=solid,fillcolor=lithuaniaRed](0,0)(25,5)


\end{pspicture}
\end{document}
