# Changing the color a the title frame

\documentclass[xcolor=dvipsnames]{beamer}
\definecolor{myblue}{rgb}{0.00,0.00,0.50}

\setbeamercolor{title}{bg=myblue!80!white}
\setbeamerfont{frametitle}{series=\mdseries}

\usecolortheme[named=blue]{structure}
\usefonttheme[onlymath]{serif} % rendre l'Ã©criture math plus beau (no necessary samcarter)
%%%%%%%%%%%%%%%%%%%%%%%%%\usepackage%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%-----
\usepackage{pifont} %bouni
%-----bclogo--------------
%\usepackage{soul} %suligne dans Bclogo
%\setul{}{1.5pt}
\usepackage[tikz]{bclogo}
%\colorlet{bctitle}{Maroon}
%\renewcommand\bcStyleTitre[1]{\vskip-0.8em\bfseries\color{bctitle}\ul{#1}\vskip-0.7em}
%-----
%-----
\setlength{\fboxsep}{7pt}
\begin{center}
\end{center}}
%--------------------

%----------pabox----------
\usepackage[most]{tcolorbox}

\newtcolorbox{mybox}[2][]{%
colback=bg,
colframe=blue!75!black,
fonttitle=\bfseries,
coltitle=blue!75!black,
colbacktitle=bg,
enhanced,
attach boxed title to top left={yshift=-1.2mm, xshift=2mm},
title=#2,
#1}
%--------------------
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%------------------------\AtBeginSubsection[]----------------------
\AtBeginSubsection[]{
\transsplitverticalout
\tableofcontents[currentsection,currentsubsection]
\end{frame}
}

%%%------begin Warsaw----------------------------------
%\usetheme{Warsaw}
%------
%-----------------------------footline-----------------------------
\setbeamertemplate{footline}{
\leavevmode%
\hbox{%
\end{beamercolorbox}%
%            \hspace*{3em}
\end{beamercolorbox}%
\end{beamercolorbox}%
}%
\vskip0pt%
}

%%%%%%%%%%%%%%%%%%%Title and author%%%%%%%%%%%%%%%%%
\title[Title of the talk]{Title of the talk}
\author[Author(University of ..)]{Author}

%%------------------%%%%%%%%%%%%%%%%%%
\begin{document}
%%%%%%%%%%%%%%%%%%

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

\maketitle{}

\end{frame}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{one}
\subsection{one}
\begin{frame}{The operator norm}

\end{frame}
\subsection{two}
\subsection{tree}
\section{two}

\section{three}

\end{document}


I want to use the color myblue in the head and bottom. Also I hope that the number of the slide will be like Author(University of ..).

In the following shortened MWE, I have used \setbeamercolor{page number in head/foot}{bg=black,fg=white} to get a white page number on a black background (please compare with \setbeamercolor{author in head/foot}{bg=black}, the settings for the author). In order to color the background of the title in the color myblue, I have changed \setbeamercolor{title in head/foot} from {bg=blue} to {bg=myblue} and added \setbeamercolor{frametitle}{bg=myblue}:

\documentclass[xcolor=dvipsnames]{beamer}
\definecolor{myblue}{rgb}{0.00,0.00,0.50}

\setbeamercolor{title}{bg=myblue!80!white}
\setbeamerfont{frametitle}{series=\mdseries}

\usecolortheme[named=blue]{structure}
\usefonttheme[onlymath]{serif}

\setbeamertemplate{footline}{
\leavevmode%
\hbox{%
\end{beamercolorbox}%
%            \hspace*{3em}
\end{beamercolorbox}%
\end{beamercolorbox}%
}%
\vskip0pt%
}

\setbeamercolor{frametitle}{bg=myblue}