\documentclass[12pt]{article}

\usepackage{pstricks} % To use the standard "xcolor" package with PSTricks
\usepackage{pst-node}
\usepackage{pst-plot}

\pagestyle{empty}

\begin{document}
\psset{unit=5mm,linewidth=.1}

\begin{center}
\begin{figure}
\begin{pspicture}(-5,5)(5,5) % -.3 due to the coordinates under Ox
\SpecialCoor

% \psaxes{->}(0,0)(-5,-5)(5,5)

\pspolygon[linestyle=none,fillcolor=green,fillstyle=solid](-5,5)(0,0)(5,5)
\rput(0,3){\psframebox[linestyle=none]{?}}

\psline[linecolor=red](-5,-5)(5,5)
\psline[linecolor=red](-5,5)(5,-5)


\rput(-3,0){\psframebox[linecolor=white]{$\mathcal{R}_1$}}
\rput(3,0){\psframebox[linecolor=white]{$\mathcal{R}_2$}}
\rput(0,-3){\psframebox[linecolor=white]{$\mathcal{R}_3$}}

\psline[arrows=<->](-4,-3)(-3,-4)
\rput(-5,-3){\psframebox[linecolor=white]{$\mathcal{C}_1$}}
\rput(-3,-5.5){\psframebox[linecolor=white]{Not $\mathcal{C}_1$}}

\psline[arrows=<->](4,-3)(3,-4)
\rput(5,-3){\psframebox[linecolor=white]{$\mathcal{C}_2$}}
\rput(3,-5.5){\psframebox[linecolor=white]{Not $\mathcal{C}_2$}}



\end{pspicture}
\end{figure}
\end{center}

\end{document}