Are beamer, hhline, and [table]{xcolor} incompatible?
as samcarter commented
\documentclass[xcolor=table]{beamer}
\usepackage{makecell, multirow}
\renewcommand\theadfont{\normalsize\bfseries\color{white}}
\renewcommand{\theadgape}{}
\usepackage{hhline}
\makeatletter
\let\zz\reset@color
\def\reset@color{\kern\z@\zz}
\makeatother
\begin{document}
\begin{frame}
\frametitle{test}
\centering
\setlength\arrayrulewidth{2pt}
\arrayrulecolor{yellow}
\def\clinecolor{\hhline{>{\arrayrulecolor{yellow}}--%
>{\arrayrulecolor{gray}}-}}
\setlength\extrarowheight{2pt}
\begin{tabular}{ c | c | c }%
\rowcolor{gray}
\multicolumn{2}{c|}{\thead{AAA -- BBBB}} & \\
\clinecolor
\rowcolor{gray}
\color{white} AAA & \color{white} BBB & \multirow{-2}{*}{\thead{CCC}} \\
\hhline{>{\arrayrulecolor{yellow}}-|-|-}
\rowcolor{gray!25}
aaa & bbb & ccc \\
\hline
\rowcolor{gray!25}
ddd & eee & fff \\
\hhline{|-|-|-|}
\end{tabular}
\end{frame}
\end{document}
Use booktabs
instead – more precisely set \above/belowrulesep
to 0pt
and use \midrule
:
\documentclass[xcolor=table]{beamer}
\usepackage{makecell, multirow}
\usepackage{booktabs}
\renewcommand\theadfont{\normalsize\bfseries\color{white}}
\renewcommand{\theadgape}{}
\begin{document}
\begin{frame}
\frametitle{test}
\centering
\setlength\arrayrulewidth{2pt}
\setlength\extrarowheight{2pt}
\setlength\belowrulesep{0pt}\setlength\aboverulesep{0pt}
\setlength\lightrulewidth{2pt}
\arrayrulecolor{yellow}
\begin{tabular}{ c | c | c }%
\rowcolor{gray}
\multicolumn{2}{c|}{\thead{AAA -- BBBB}} & \\
\midrule
\rowcolor{gray}
\color{white} AAA & \color{white} BBB & \multirow{-2}{*}{\thead{CCC}} \\
\midrule
\rowcolor{gray!25}
aaa & bbb & ccc \\
\midrule
\rowcolor{gray!25}
ddd & eee & fff \\
\end{tabular}
\end{frame}
\end{document}