\begin{tabular}{c | c | c | c | c | c}
\rowcolor{gray!30} \cellcolor{gray} & v1 & v2 & v3 & v4 & v5 \\
\hline
\cellcolor{gray!30} v1 & \cellcolor{gray!30} & & & & \\
\hline
\cellcolor{gray!30} v2 & & \cellcolor{gray!30} & & & \\
\hline
\cellcolor{gray!30} v3 & & & \cellcolor{gray!30} & & \\
\hline
\cellcolor{gray!30} v4 & & & & \cellcolor{gray!30} & \\
\hline
\cellcolor{gray!30} v5 & & & & & \cellcolor{gray!30} \\
\end{tabular}