我正在 Overleaf 中使用 LaTeX，遇到了以下问题：
当我把这个代码片段：
\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
commentstyle=\color[rgb]{0.4,0.4,0.4}, % comment style
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}
我收到一个错误：
Package xcolor Error: Undefined color `gray45'.
该错误显示如下行：
#hostname
我不太明白发生了什么。有人能告诉我吗？
答案1
我不知道您的问题实际上出现在哪里。
您不应该加载color-package 三次（两次为color，一次为xcolor）。我删除了其中两个。另外，您的 MWE 缺少\documentclass和\begin{document}... \end{document}。我添加了它们，对我来说一切都很好。
\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
commentstyle=\color[rgb]{0.4,0.4,0.4}, % comment style
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}
答案2
通过定义名为“gray45”的颜色解决了错误，如下所示：
\definecolor{gray45}{rgb}{0.2, 0.5, 0.478}
似乎在列表框中输入字符 # 时，它会将其编译为颜色，但实际上并非如此。但是，正如我所说，定义颜色后错误就解决了。