I was wondering whether it is possible to change beamer's color theme locally only for a couple of slides. I am teaching a graduate class and sometimes include summaries of topics that may be relevant only to graduate students who actively do research in that specific area. I would like to distinguish these slides using a more greyish color scheme so that students who don't come to class later know that these slides are not exam relevant.
I noticed that \usecolortheme{colortheme} works only in the preamble and that the frame environment has no options to change its color theme. I know I could generate those slides from a separate .tex file and concatenate the slides later but then I would lose some interactive functionality. Is there any workaround that allows me to change the color theme locally?
Edit: I guess what Schrödinger's cat is suggesting is to define structure and section in head/foot using your own colors, to define every other beamercolor by inheriting from those two, and to create custom commands as follows to switch between the themes:
\newcommand{\maintheme}{
\setbeamercolor{structure}{fg=main,bg=secondary}
\setbeamercolor{section in head/foot}{fg=main,bg=secondarylight}
}
\newcommand{\sidetheme}{
\setbeamercolor{structure}{fg=white,bg=gray}
\setbeamercolor{section in head/foot}{fg=white,bg=lightgray}
}
Great idea, but I had some unexpected behavior where colors either did not change (background color of sectionnavigation), colors changed one slide late (itemize bullets) or to a different color than originally defined (enumerate item). Do you have any idea what this is so?
I apologize that the MWE is a bit lengthy, mostly to include a block, an itemize, and an enumerate environment on each slide:
\documentclass[10pt]{beamer}
\usetheme{Frankfurt}
\definecolor{main}{rgb}{0.4675, 0.11, 0.115}
\definecolor{secondary}{rgb}{0.75, 0.625, 0.15}
\definecolor{secondarylight}{rgb}{0.896, 0.83, 0.56}
\setbeamercolor{structure}{fg=main,bg=secondary}
\setbeamercolor{section in head/foot}{fg=main,bg=secondarylight}
\setbeamercolor{frametitle}{parent=structure}
\setbeamerfont{frametitle}{size=\large}
\setbeamercolor{title}{parent=section in head/foot}
\setbeamercolor{item}{fg=structure.bg}
\setbeamertemplate{enumerate items}[default]
\setbeamercolor{enumerate item}{parent=structure}
\setbeamertemplate{blocks}[rounded][shadow=true]
\setbeamerfont{block title}{series=\bfseries}
\setbeamercolor{block title}{fg=structure.fg,bg=structure.bg}
\setbeamercolor{block body}{bg=white}
\beamertemplatenavigationsymbolsempty
\newcommand{\sidetheme}{
\setbeamercolor{structure}{fg=white,bg=gray}
\setbeamercolor{section in head/foot}{fg=white,bg=lightgray}
\setbeamercolor{item}{fg=section in head/foot.bg}
\setbeamercolor{enumerate item}{fg=structure.bg}
}
\newcommand{\maintheme}{
\setbeamercolor{structure}{fg=main,bg=secondary}
\setbeamercolor{section in head/foot}{fg=main,bg=secondarylight}
\setbeamercolor{item}{fg=structure.bg}
\setbeamercolor{enumerate item}{parent=structure}
}
\title{Changing Color Schemes Locally}
\begin{document}
\thispagestyle{empty}
\maketitle
\setcounter{beamerpauses}{1}
\setcounter{framenumber}{0}
\section{Topic 1}
\begin{frame}
\frametitle{Information Central to the Course}
\begin{definition}
Some very insightful definition.
\begin{enumerate}
\item Yada
\item Yada
\end{enumerate}
\end{definition}
\medskip
\textbf{Interpretation:}
\begin{itemize}
\item Important point.
\item Another important point.
\end{itemize}
\end{frame}
\sidetheme
\begin{frame}
\frametitle{Additional Information}
\begin{definition}
Some very insightful definition.
\begin{enumerate}
\item Yada
\item Yada
\end{enumerate}
\end{definition}
\medskip
\textbf{Interpretation:}
\begin{itemize}
\item Important point.
\item Another important point.
\end{itemize}
\end{frame}
\begin{frame}
\frametitle{Additional Information}
\begin{definition}
Some very insightful definition.
\begin{enumerate}
\item Yada
\item Yada
\end{enumerate}
\end{definition}
\medskip
\textbf{Interpretation:}
\begin{itemize}
\item Important point.
\item Another important point.
\end{itemize}
\end{frame}
\maintheme
\section{Topic 2}
\begin{frame}
\frametitle{Information Central to the Course}
\begin{definition}
Some very insightful definition.
\begin{enumerate}
\item Yada
\item Yada
\end{enumerate}
\end{definition}
\medskip
\textbf{Interpretation:}
\begin{itemize}
\item Important point.
\item Another important point.
\end{itemize}
\end{frame}
\end{document}
