beamer: inserire colorbox nella titlepage

Salve

sto creando una presentazione con una figura come background della prima slide.

se Osservate il codice il titolo appare dentro un colorbox, io vorrei ottenere lo stesso per gli elementi

\author
\date
\institute

ho provato ad usare il comando \colorbox ma mi da errore in fase di compilazione.

qualcuno mi darebbe una mano?

`
\documentclass[9pt]{beamer}

% Setup appearance:
\usetheme{Antibes}
%\usetheme{Copenhagen}
%\usetheme{Darmstadt}
\usefonttheme[onlysmall]{structurebold}
\useoutertheme{infolines}
\setbeamerfont*{frametitle}{size=\normalsize,series=\bfseries}
\setbeamertemplate{navigation symbols}{}
\usecolortheme[rgb={0.5,0,0.5}]{structure}
%\logo{\includegraphics[height=0.9cm,keepaspectratio]{logo_corso_new}}
%
\setbeamertemplate{headline} {
\leavevmode%
\hbox to12cm{\insertlogo}
}

\setbeamertemplate{sidebar right}{
\vfill
% \llap{\insertlogo\hskip0.1cm}%
% \vskip2pt%
\llap{\usebeamertemplate***{navigation symbols}\hskip0.2cm}%
\vskip2pt%
}

\definecolor{mypurple}{rgb}{0.5, 0.0, 0.50}

% Standard packages

%\usepackage{pgf,pgfarrows,pgfnodes,pgfautomata,pgfheaps,pgfshade}
\usepackage{amsmath,amssymb}
\usepackage[italian]{babel}
\usepackage[latin1]{inputenc}
\usepackage{times}
\usepackage[T1]{fontenc}

% Author, Title, etc.

\title[my talk]
{%
% \textcolor{red}{title of my work}%
title of my work
}

\author[me]
{
my name\inst{1}
}

\institute[myinst] {
\inst{1}%
\textcolor{red}{my university\\ \texttt{mymail}}
}

\date[that day]
{%\today
that day
}
%

\begin{document}

%———– titlepage ———————————————-%
{ % brace to limit the scope of \setbeamertemplate
\setbeamertemplate{navigation symbols}{} % optionally hide naviation buttons

\setbeamertemplate{background canvas}{\includegraphics
[width=1.0\paperwidth,height=1.0\paperheight]{JET_vessel-split-image.jpg}}
\begin{frame}
\titlepage
\end{frame}
}

\begin{frame}

\end{frame}

\end{document}
`