Changing navigation bar's color in a latex beamer with Frankfurt theme

Question

I would like to change the color of the black navigation bar, which is at the top of the slide. Here is a picture :

Answer 1

You can change the background colour of the headline like this:

\documentclass{beamer}

\usetheme{Frankfurt}

\setbeamercolor{section in head/foot}{bg=red}

\begin{document}

\section{title}
\begin{frame}
\frametitle{title}
    abc
\end{frame} 
    
\end{document}