\usepackage {colortbl}
\newcommand\panel[1]{\multicolumn{1}%
{>{\columncolor{white}}#1}}
\colorbox{magenta}{%
\arrayrulecolor{black}
\begin{tabular}{lrr}
\large\textbf{Table title}\\[2mm]
\textbf{Description}
& \textbf{Column 1}
& \textbf{Column 2}\\[1mm]
Row one & mmmmm & mmmm \\
Row two & mmmm & mmm \\
\panel{l}{Row three}
& \panel{r}{mmmmm}
& \panel{r}{mmmmm} \\
Row four& mmmmm & mmmm \\ \cline{2-3}
Totals & mmmmm & mmmmm
\end{tabular}}
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