Beamer。块。如何重置 \setbeamercolor{block title} 和 \setbeamercolor{block body}？

Question

使用自定义颜色块后

\setbeamercolor{block title}{use=structure,fg=white,bg=red!75}
\setbeamercolor{block body}{use=structure,fg=black,bg=red!30}

如何重置为初始值？

\frame
{
\frametitle{Hello}
\framesubtitle{Hi}
\setbeamercolor{block title}{use=structure,fg=white,bg=black}
\setbeamercolor{block body}{use=structure,fg=black,bg=gray!60}
\begin{block}{Say you will}
\begin{itemize}
  \item One
  \item Two
\end{itemize}
%  HOW TO RESET THE COLORS TO THE ORIGINAL VALUES
\end{block}
%
%
\begin{block}{Actividades}
\begin{enumerate}
\footnotesize{
  \item Me and you
  \item You and me  
}
\end{enumerate}
\end{block}
}

Answer 1

只需将颜色修改放在{}

\documentclass{beamer}

\begin{document}

\frame
{
    \frametitle{Hello}
    \framesubtitle{Hi}

    {
    \setbeamercolor{block title}{use=structure,fg=white,bg=black}
    \setbeamercolor{block body}{use=structure,fg=black,bg=gray!60}
    \begin{block}{Say you will}
        \begin{itemize}
            \item One
            \item Two
        \end{itemize}
        %  HOW TO RESET THE COLORS TO THE ORIGINAL VALUES
    \end{block}
    }
    %
    %
    \begin{block}{Actividades}
        \begin{enumerate}
            \footnotesize{
                \item Me and you
                \item You and me  
            }
        \end{enumerate}
    \end{block}
}

\end{document}