# Package xcolor Error: Undefined color gray45'. error when using lstlistings in LaTeX

I am working with LaTeX in Overleaf, and I have the next problem:

When I put this code fragment:

\usepackage{ucs}
\usepackage[utf8x]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{listings}
\usepackage[usenames, dvipsnames]{color}
\usepackage{colortbl}
\usepackage{xcolor}
\usepackage{color}

\lstset{ %
backgroundcolor=\color{white},   % choose the background color; you must add \usepackage{color} or \usepackage{xcolor}
basicstyle=\footnotesize\ttfamily,        % the size of the fonts that are used for the code
breakatwhitespace=false,         % sets if automatic breaks should only happen at whitespace
breaklines=true,                 % sets automatic line breaking
extendedchars=true,              % lets you use non-ASCII characters; for 8-bits encodings only, does not work with UTF-8
frame=single,                      % adds a frame around the code
keepspaces=true,                 % keeps spaces in text, useful for keeping indentation of code (possibly needs columns=flexible)
keywordstyle=\color[rgb]{0.18,0.28,0.75},       % keyword style
language=Python,                 % the language of the code
numberstyle=\color[rgb]{0.7,0.1,0.4}, % the style that is used for the line-numbers
rulecolor=\color{black},         % if not set, the frame-color may be changed on line-breaks within not-black text (e.g. comments (green here))
stringstyle=\color[rgb]{1,0.6,0.2},     % string literal style
showspaces=false,                % show spaces everywhere adding particular underscores; it overrides 'showstringspaces'
showstringspaces=false,          % underline spaces within strings only
showtabs=false,                  % show tabs within strings adding particular underscores
stepnumber=2,                    % the step between two line-numbers. If it's 1, each line will be numbered
tabsize=2,                     % sets default tabsize to 2 spaces
}

\begin{lstlisting}[language=bash,caption={Establecer hostname}]

#hostname

\end{lstlisting}


I am getting an error:

Package xcolor Error: Undefined color gray45'.


That error is shown in line:

#hostname


I don't really understand what is happening. Could anyone tell me, please?

• When I remove # character, all seems to be fine... – jartymcfly Jan 24 '17 at 8:30
• You're writing in python where # indicates a comment, and gray45 is set up as your comment colour -- so making text not a comment would stop the error but spoil the listing. – Chris H Jan 24 '17 at 8:50

I don't know, where your problem actually arises.

You should not load the color-package three times, (two times as color, one time as xcolor). I removed two of them. Also, you MWE lacks a \documentclass and \begin{document} ... \end{document}. I added them and everything is fine to me.

\documentclass{article}

\usepackage[utf8x]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{listings}
\usepackage[usenames, dvipsnames]{color}

\lstset{ %
backgroundcolor=\color{white},   % choose the background color; you must add \usepackage{color} or \usepackage{xcolor}
basicstyle=\footnotesize\ttfamily,        % the size of the fonts that are used for the code
breakatwhitespace=false,         % sets if automatic breaks should only happen at whitespace
breaklines=true,                 % sets automatic line breaking
extendedchars=true,              % lets you use non-ASCII characters; for 8-bits encodings only, does not work with UTF-8
frame=single,                      % adds a frame around the code
keepspaces=true,                 % keeps spaces in text, useful for keeping indentation of code (possibly needs columns=flexible)
keywordstyle=\color[rgb]{0.18,0.28,0.75},       % keyword style
language=Python,                 % the language of the code
numberstyle=\color[rgb]{0.7,0.1,0.4}, % the style that is used for the line-numbers
rulecolor=\color{black},         % if not set, the frame-color may be changed on line-breaks within not-black text (e.g. comments (green here))
stringstyle=\color[rgb]{1,0.6,0.2},     % string literal style
showspaces=false,                % show spaces everywhere adding particular underscores; it overrides 'showstringspaces'
showstringspaces=false,          % underline spaces within strings only
showtabs=false,                  % show tabs within strings adding particular underscores
stepnumber=2,                    % the step between two line-numbers. If it's 1, each line will be numbered
tabsize=2,                     % sets default tabsize to 2 spaces
}

\begin{document}

\begin{lstlisting}[language=bash,caption={Establecer hostname}]

#hostname

\end{lstlisting}
\end{document}


The error was solved defining a color named 'gray45', like this:

\definecolor{gray45}{rgb}{0.2, 0.5, 0.478}


It seems that when entering a character # into a listings box, it ties to compile it as a color, when it is not. But, as I said, defining the color the error was solved.