\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows}
\usetikzlibrary{snakes}
\usetikzlibrary{positioning}
\usepackage{verbatim}


\begin{document}

\begin{tikzpicture}[scale=1.5, on grid]
 \draw [help lines](-2,-2) grid (2,2);


\draw[-triangle 45, color=blue] (-0.75,0.5) -- (0.75,-0.5) node[sloped,below] { $-$};
\draw[-triangle 45, color=red] (0.75,0.5) -- (-0.75,-0.5) node[sloped,below] { $+$};

\node[] at (0,0) {$\left( {\begin{array}{*{20}c}
   {a_{11} } & {a_{12} }  \\
   {a_{21} } & {a_{22} }  \\
\end{array}} \right)
$};



\end{tikzpicture}
\end{document} 