如何生成定理，其中标题和定理主体的颜色可能不同？

Question

我已经尝试过以下代码，

\documentclass{article}
\usepackage{amsthm,amssymb,xcolor}
\theoremstyle{plain}
\newtheorem{thm}{Theorem}
\begin{document}
\begin{color}{blue}{\begin{thm}\begin{color}{red}{The     theorem.}\end{thm}}\end{color}
\end{document}

但它不起作用。所以我的问题如下，

1. 我该如何解决这个问题？例如，以下代码是什么，

标题将呈现蓝色，定理主体将呈现红色。

2. book如果文档类是或，则相同的代码是什么memoir？

Answer 1

最简单的方法是使用thmtools界面。

\documentclass{article}
\usepackage{amsthm,thmtools,xcolor}

\declaretheoremstyle[
  headfont=\color{blue}\normalfont\bfseries,
  bodyfont=\color{red}\normalfont\itshape,
]{colored}

\declaretheorem[
  style=colored,
  name=Theorem,
]{thm}

\begin{document}

\begin{thm}
The theorem.
\end{thm}

\end{document}

Answer 2

您可以通过声明来实现结果，newtheoremstyle如文档第 9 页所述amsthm：

% declare a new theorem style
\newtheoremstyle{mystyle}%
{3pt}% Space above
{3pt}% Space below 
{\itshape\color{red}}% Body font
{}% Indent amount
{\bfseries\color{blue}}% Theorem head font
{.}% Punctuation after theorem head
{.5em}% Space after theorem head
{}% Theorem head spec (can be left empty, meaning ‘normal’)

然后您可以将其用作：

% use the new theorem style
\theoremstyle{mystyle}
\newtheorem{thm}{Theorem}

这是一个完整的例子，输出与 egreg 的回答一样。

% arara: pdflatex
 \documentclass{book}
\usepackage{amsthm,xcolor}

% declare a new theorem style
\newtheoremstyle{mystyle}%
{3pt}% Space above
{3pt}% Space below 
{\itshape\color{red}}% Body font
{}% Indent amount
{\bfseries\color{blue}}% Theorem head font
{.}% Punctuation after theorem head
{.5em}% Space after theorem head 
{}% Theorem head spec (can be left empty, meaning ‘normal’)

% use the new theorem style
\theoremstyle{mystyle}
\newtheorem{thm}{Theorem}

\begin{document}
\begin{thm}
The theorem.
\end{thm}
\end{document}