[Tex/LaTex] Beamer: changing footline background color

beamercolorheader-footer

I would like to make the footline color black and the text white. I found this: Beamer: Background Color for Footline
but didn't understand how it applied to my example.

\documentclass{beamer}
\usetheme{Frankfurt}
\usecolortheme{dove}
\setbeamercolor{section in head/foot}{fg=white, bg=black}

\makeatletter
\setbeamertemplate{footline}
{
  \leavevmode%
  \hbox{%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,center]{author in head/foot}%
    \usebeamerfont{author in head/foot}\insertshortauthor~~\beamer@ifempty{\insertshortinstitute}{}{(\insertshortinstitute)}
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,center]{title in head/foot}%
    \usebeamerfont{title in head/foot}\insertshorttitle
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,right]{date in head/foot}%
    \usebeamerfont{date in head/foot}\insertshortdate{}\hspace*{2em}
    \insertframenumber{} / \inserttotalframenumber\hspace*{2ex} 
  \end{beamercolorbox}}%
  \vskip0pt%
}
\makeatother

\begin{document}

    \section{Introduction}      
        \begin{frame}{Frame}

        \end{frame}

\end{document}

Best Answer

Since you declare

\setbeamercolor{section in head/foot}{fg=white, bg=black}

you can use the section in head/foot color for the three beamercolorboxes forming the footline:

\documentclass{beamer}
\usetheme{Frankfurt}
\usecolortheme{dove}
\setbeamercolor{section in head/foot}{fg=white, bg=black}

\makeatletter
\setbeamertemplate{footline}
{
  \leavevmode%
  \hbox{%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,center]{section in head/foot}%
    \usebeamerfont{author in head/foot}\insertshortauthor~~\beamer@ifempty{\insertshortinstitute}{}{(\insertshortinstitute)}
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,center]{section in head/foot}%
    \usebeamerfont{title in head/foot}\insertshorttitle
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,right]{section in head/foot}%
    \usebeamerfont{date in head/foot}\insertshortdate{}\hspace*{2em}
    \insertframenumber{} / \inserttotalframenumber\hspace*{2ex} 
  \end{beamercolorbox}}%
  \vskip0pt%
}
\makeatother

\title{The Title}
\author{The Author}
\institute{The Institute}

\begin{document}

\section{Introduction}      
\begin{frame}{Frame}
test
\end{frame}

\end{document}

enter image description here

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