Création d'un language listings pour les expressions régulières

\documentclass[12pt]{article}

\usepackage{listings}
\usepackage{xcolor}

\lstdefinelanguage{regex}{
  commentstyle=\color{gray},
  keywords={},
  otherkeywords={^, \{, \}, ?, +},
  alsoletter={},
  basicstyle=\ttfamily,
  keywordstyle=\bfseries\color{green},
  breakatwhitespace=false,
  breaklines=true,
  captionpos=b,
  showspaces=false,
  showstringspaces=true,
  literate=%
  *{0}{{{\color{red}0}}}1
  {1}{{{\color{red}1}}}1
  {2}{{{\color{red}2}}}1
  {3}{{{\color{red}3}}}1
  {4}{{{\color{red}4}}}1
  {5}{{{\color{red}5}}}1
  {6}{{{\color{red}6}}}1
  {7}{{{\color{red}7}}}1
  {8}{{{\color{red}8}}}1
  {9}{{{\color{red}9}}}1
  {(}{{{\bfseries\color{blue}(}}}1
  {)}{{{\bfseries\color{blue}\)}}}1
}

\begin{document}

\begin{lstlisting}[language=regex]
  ((a+b){4,5})*c? + [^ab{?]{3}
\end{lstlisting}

\end{document}