[OS X TeX] \rowcolors undefined control sequence

[BenBehr]

Hi,

I have tried to use the \rowcolors... command. I have used the  
following code:

\documentclass[a4paper,11pt]{scrartcl} % Ausgangspapiergroesse
\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage[latin1,ansinew]{inputenc}
\usepackage{color}
\usepackage{colortbl}
\usepackage{array}
\usepackage{tabularx}
\usepackage{xcolor}
\begin{document}
Hallo,
in der folgenden Tabelle soll mit \rowcolors ab der 3. Zeile die
(Grund)Farbe gewechselt werden. Funzt aber nicht.
Wo gibt es berhaupt eine "Beschreibung" von \rowcolors? In colortbl.sty
find ich nichts.
\rowcolors[]{1}{red!20}{red!10}\rowcolors[]{3}{blue!20}{blue!10}
\begin{tabular}{ r p{4cm} l}\hline
\textbf{Datum} &\textbf{ Ereignis} &\textbf{ Verweis }\\\hline
& & \\
& & \\
& & \\
&& \\
& & \\
&& \\
\end{tabular}
\end{document}

However this is not working for me. I keep getting the Error Undefined  
control sequence \rowcolors. I also could not find this command in the  
documentation of the package colortbl but i found this command in a  
lecture on Latex and in the internnet in the above exsample.

Do you have any suggestions what might be wrong?

Thanks,
Ben