Beamer : Different colors for section in toc and section in head/foot / Empty line below headline with Ilmenau

Question

I'm creating a Beamer presentation and I want to include section titles as links in the headline with hyperref. I also want the TOC to be displayed at the beginning of each section with the section titles as blue links. I use the theme Ilmenau.

When I do that, the section titles appear in blue in both the TOC on the frame and the TOC on the navigation bar. Then, section titles cannot be read in the navigation bar.

Is there something I can do ?

I would also like to remove the empty line between the headline and the frame title because I will not use subsections. How to do it ?

I'm sorry I'm a beginner with Beamer.

Here is a reproducible example :

\documentclass{beamer}
\usepackage[UTF8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[francais]{babel}
\usepackage{lmodern}
\usepackage{hyperref}
\usepackage{url}

\def\bibfont{\footnotesize}
\addto\captionsfrench{\def\contentsname{}}
\hypersetup{
        colorlinks = true,
        linkcolor=blue,
        urlcolor=blue
}

\usetheme{Ilmenau}

\title[Meeting]{Meeting}
\subtitle{Subject of the meeting}
\author[M. Dupont]{P. Dupont\inst{1,2,3} \and P. Dupond\inst{1} \and E. Dupond\inst{2} \and F. Dupont\inst{3}}
\institute[Dupont's Institution]{
    \inst{1}
    Dupont Lab, France\\
    Univ. of Dupont
    \and
    \inst{2}
    Dupond, France\\
    Univ. of Dupond
    \and
    \inst{3}
    Dupond Factory, Paris
}
\date{17/09/2018}


\addtobeamertemplate{navigation symbols}{}{%
        \usebeamerfont{footline}%
        \usebeamercolor[fg]{footline}%
        \hspace{1em}%
        \insertframenumber/\inserttotalframenumber
}
\setbeamercolor{footline}{fg=blue}
\setbeamercolor{section in head/foot}{fg=white}

\begin{document}


\frame{\titlepage}

\AtBeginSection[]
{
 \begin{frame}
        \frametitle{Section's outline}
        \tableofcontents[currentsection]
    \end{frame}
    %\setbeamercolor{section in toc}{fg=black}
}





%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{Introduction}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\begin{frame}{First subject}

\end{frame}

\begin{frame}{Second subject}

\end{frame}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{Organization}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{frame}{First subject}

\end{frame}

\begin{frame}{Second subject}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{Development}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{frame}{First subject}

\end{frame}

\begin{frame}{Second subject}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{Conclusion}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{frame}{First subject}

\end{frame}

\begin{frame}{Second subject}

\end{frame}


\end{document}

Answer 1

• You can change the colour of the toc entries with \setbeamercolor{section in toc}{fg=structure}

  (I recommend to use the colour structure instead of blue, as blue creates a terrible colour clash with the surrounding elements)

• to hide the subsection navigation:

  \makeatletter
  \beamer@theme@subsectionfalse
  \makeatother
  

• you don't need to load the hyperref package with beamer, beamer already provides it for you

• the babel option francais is deprecated, use french instead

---

\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[french]{babel}
\usepackage{lmodern}

\def\bibfont{\footnotesize}
\addto\captionsfrench{\def\contentsname{}}

\usetheme{Ilmenau}

\makeatletter
\beamer@theme@subsectionfalse
\makeatother

\title[Meeting]{Meeting}
\subtitle{Subject of the meeting}
\author[M. Dupont]{P. Dupont\inst{1,2,3} \and P. Dupond\inst{1} \and E. Dupond\inst{2} \and F. Dupont\inst{3}}
\institute[Dupont's Institution]{
    \inst{1}
    Dupont Lab, France\\
    Univ. of Dupont
    \and
    \inst{2}
    Dupond, France\\
    Univ. of Dupond
    \and
    \inst{3}
    Dupond Factory, Paris
}
\date{17/09/2018}


\addtobeamertemplate{navigation symbols}{}{%
        \usebeamerfont{footline}%
        \usebeamercolor[fg]{footline}%
        \hspace{1em}%
        \insertframenumber/\inserttotalframenumber
}
\setbeamercolor{footline}{fg=structure}
\setbeamercolor{section in head/foot}{fg=white}


\setbeamercolor{section in toc}{fg=structure}

\begin{document}


\frame{\titlepage}

\AtBeginSection[]
{
 \begin{frame}
        \frametitle{Section's outline}
        \tableofcontents[currentsection]
    \end{frame}
    %\setbeamercolor{section in toc}{fg=black}
}





%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{Introduction}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\begin{frame}{First subject}

\end{frame}

\begin{frame}{Second subject}

\end{frame}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{Organization}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{frame}{First subject}

\end{frame}

\begin{frame}{Second subject}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{Development}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{frame}{First subject}

\end{frame}

\begin{frame}{Second subject}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{Conclusion}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{frame}{First subject}

\end{frame}

\begin{frame}{Second subject}

\end{frame}


\end{document}