Xcolor
Try xcolor You can even set alternating colors
\documentclass[table]{scrartcl}
\usepackage[ngerman]{babel}
\usepackage{xcolor}
\begin{document}
\colorbox{red}{
\begin{tabular}{|lp{10cm}|}
\hline
\multicolumn{2}{|c|}{\textbf{Test}}\\
\hline
Test: & Test\\
Test: & Test\\
\hline
\end{tabular}
}
\rowcolors*{1}{red}{red}
\begin{tabular}{|lp{10cm}|}
\hline
\multicolumn{2}{|c|}{\textbf{Test}}\\
\hline
Test: & Test\\
Test: & Test\\
\hline
\end{tabular}
\end{document}

(Just for my sake i'd like to say that typographically spoken vertical rules are odd. Avoid them. And i stripped \mbox{}.. cause i can't see the purpose. )
Tabu
The tabu Package provides you with some more convenient commands
\documentclass[table]{scrartcl}
\usepackage{xcolor}
\usepackage{tabu}
\begin{document}
\taburowcolors [1] 7 {green .. brown}
\begin{tabu}{|lp{10cm}|}
\hline
\multicolumn{2}{|c|}{\textbf{Test}}\\
\hline
Test: & Test\\
Test: & Test\\
Test: & Test\\
Test: & Test\\
Test: & Test\\
Test: & Test\\
\hline
\end{tabu}
\end{document}
