\documentclass{article}
\usepackage{threeparttable}
\usepackage{multirow}
\usepackage{booktabs}
\usepackage{xcolor}
\begin{document}
\begin{table}[!ht]
\setlength\tabcolsep{0pt}
\centering
\begin{threeparttable}
\begin{tabular}{@{\extracolsep{2ex}}*{5}{ccccc}}
\toprule
\textbf{value1} & \textbf{value2} & \textbf{group1} & \textbf{group3} & \textbf{group2} \\
\midrule
1 & a & a & c & e \\
2 & b & a & c & f \\
3 & c & a & d & e \\
4 & a & a & d & f \\
5 & b & b & c & e \\
6 & c & b & c & f \\
7 & a & b & d & e \\
8 & b & b & d & f \\
\bottomrule
\end{tabular}
\end{threeparttable}
\end{table}
\end{document}