title: Fontcolor in listing
body: <p>I want to write a listing for python code. My problem, the zero by <code>x = SUM('ZM_test'[testcol 0AN])</code> is in black fontcolor and not in green. My style settings for the listing looks like this:</p>
  <pre><code>\documentclass[12pt,a4paper]{report}
  \usepackage[utf8]{inputenc}
  \usepackage[german]{babel}
  \usepackage[left=4cm,right=3cm,top=2.5cm,bottom=2.5cm]{geometry}
  
  \usepackage{listings}
  \usepackage{color}
  \definecolor{keywords}{RGB}{255,0,90}
  \definecolor{comments}{RGB}{0,0,113}
  \definecolor{red}{RGB}{160,0,0}
  \definecolor{green}{RGB}{0,150,0}
  \lstset{language=Python, 
      basicstyle=\ttfamily\footnotesize, 
      keywordstyle=\color{keywords},
      commentstyle=\color{comments},
      stringstyle=\color{red},
      showstringspaces=false,
      identifierstyle=\color{green},
      %procnamekeys={def,class}
      numbers=left,
      xleftmargin=2em,
      frame=single,
      framexleftmargin=1.5em
  }
  
  \begin{document}
  \begin{lstlisting}[language=Python, caption=xy, label=xy, numbers =left, frame= lines, gobble = 0]
  x = SUM('ZM_test'[testcol 0AN])
  y = SUM('ZM_test'[testcol bAN])
  \end{lstlisting}
  \end{document}
  </code></pre>
  <p>Do you know, why the zero has the fontcolor &quot;black&quot; and not &quot;green&quot;? I want the zero green like the &quot;b&quot; in  <code>y = SUM('ZM_test'[testcol bAN])</code></p>
  <p>EDIT: That is not python code, but it should be the python style.
  Best regards
  Christian</p>