\begin{table}[htbp]
\begin{center}
\begin{tabularx}{15cm}{lXX}
  \toprule
  \rowcolor{dunkelgrau}
  \textbf{Spalte 1} & \textbf{Spalte 2} & \textbf{Spalte 3}\\
  \midrule
  \rowcolor{hellgrau1}
  \emph{XXX} & YYY & ZZZ \\
  \rowcolor{hellgrau2}
  \emph{XXX} & YYY & ZZZ \\
  \rowcolor{hellgrau1}
  \emph{XXX} & YYY & ZZZ \\
  \bottomrule
\end{tabularx}
\caption{}
\label{tab:xxx}
\end{center}
\end{table}
