%tikz
\begin{tikzpicture}[every node/.style={draw,scale=1pt,minimum width=20pt,inner sep=3pt,line width=0pt,draw=black!20}]
\matrix[row sep=2pt,column sep=2pt]
{\node[fill=black!50]{31};&
\node[fill=black!15]{32};&
\node[fill=red!80!blue!60]{33};&
\node[fill=green!80!blue!60]{34};&
\node[fill=blue!80!green!60]{35};&
\node[fill=-red!80!blue!60]{36};&
\node[fill=-green!80!blue!60]{37};&
\node[fill=-blue!80!green!60]{38};&
\node[fill=black!40]{39};&
\node[fill=black!10]{40};\\
\node[fill=-green!20]{21};&
\node[fill=-blue!20]{22};&
\node[fill=black!60]{23};&
\node[fill=black!20]{24};&
\node[fill=red!80!green!50]{25};&
\node[fill=green!80!red!50]{26};&
\node[fill=blue!80!red!50]{27};&
\node[fill=-red!80!green!50]{28};&
\node[fill=-green!80!red!50]{29};&
\node[fill=-blue!80!red!50]{30};\\
\node[fill=blue!50]{11};&
\node[fill=-red!50]{12};&
\node[fill=-green!50]{13};&
\node[fill=-blue!50]{14};&
\node[fill=black!70]{15};&
\node[fill=black!25]{16};&
\node[fill=red!20]{17};&
\node[fill=green!20]{18};&
\node[fill=blue!20]{19};&
\node[fill=-red!20]{20};\\
\node[fill=red]{1};&
\node[fill=green]{2};&
\node[fill=blue]{3};&
\node[fill=-red]{4};&
\node[fill=-green]{5};&
\node[fill=-blue]{6};&
\node[fill=black!80]{7};&
\node[fill=black!30]{8};&
\node[fill=red!50]{9};&
\node[fill=green!50]{10};\\
};
\end{tikzpicture}
