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Is it possible (using ntheorem) to change the default text colour of the proof environment (of course black) to a boldface red? I am typesetting an Analysis book, and a friend and I are looking [for content and also for stylistic purposes] for a rather unique look. Thus, we thought about having the proofs in a bold-faced red font. So, I would like to know if that is achievable? Thanks! Currently, these are how I have my theorem-like environments defined and here is a MWWE:

\documentclass[12pt,a4paper]{article}

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % %
% % % % % % % % % % % % % % % % % % % % % % % % % % % % % %
% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 

\usepackage[left=2.50cm,right=2.50cm,top=2.50cm,bottom=2.75cm]{geometry}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amstext}
\usepackage{pstricks}
\usepackage{framed}
\usepackage[amsmath,framed,thmmarks]{ntheorem}
\usepackage{textcomp}

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % %
% % % % % % % % % % % % % % %
% % % % % % % % % % % % % % % % % % % % % % % % % % % % % %

\newtheorem{Theorem}{Thm}
\theoremclass{Theorem}
\theoremstyle{break}
\shadecolor{blue}
\newshadedtheorem{thm}[Theorem]{Theorem}

\theoremclass{Theorem}
\theoremstyle{break}
\shadecolor{gray}
\newshadedtheorem{prop}[Theorem]{Proposition}

\theoremclass{Theorem}
\theoremstyle{plain}
\newframedtheorem{lem}[Theorem]{Lemma}

\theoremclass{Theorem}
\theoremstyle{plain}
\newframedtheorem{cor}[Theorem]{Corollary}


\theoremstyle{plain}
\theoremsymbol{\ensuremath{\blacktriangle}}
\theoremseparator{.}
\theoremprework{\bigskip\hrule}
\theorempostwork{\hrule\bigskip}
\newtheorem{defn}{Definition}

\theoremstyle{plain}
\theorembodyfont{\upshape}
\theoremsymbol{\ensuremath{\bullet}}
\theoremseparator{}
\newtheorem{exam}{Example}

\theoremstyle{plain}
\theorembodyfont{\upshape}
\theoremsymbol{\ensuremath{\bullet}}
\newtheorem{exer}{Exercise}[section]


\theoremheaderfont{\sc}
\theorembodyfont{\textcolor{red}}
\theoremstyle{nonumberplain}
\theoremseparator{.}
\theoremsymbol{\rule{1ex}{1ex}}
\newtheorem{proof}{Proof}

\theoremstyle{plain}
\theorembodyfont{\upshape}
\theoremsymbol{\ensuremath{\bigstar}}
\theoremseparator{.}
\newtheorem{rem}{Remark}

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %

\begin{document}

\begin{thm}[Bolzano-Weirstrass Theorem]
Every bounded sequence in $\mathbb{K}^m$ has a convergent subsequence ...
\end{thm}

\begin{proof}
We consider first the case where $\mathbb{K} = \mathbb{R}$ and prove     the  case by induction on $m \ldots$
\end{proof}

\begin{exam}\mbox{}
Let the universe be the set of real numbers. Then:
\begin{enumerate}
   \item  $(\exists x)(x \ge 3)$ is true because the truth set of $x \ge 3$ contains $3, \pi, 5$, and many other real numbers; and hence is nonempty.
   \item sdfdkjwfdwsjfdws
\end{enumerate}
\end{exam}


\begin{rem}
Note that the previous proposition is quite useful in helping us to find negations for quantified propositions.
\end{rem}


\begin{defn}[Logical Equivalence] 
Two propositions are said to be logically equivalent iff ...
\end{defn}  

\end{document}

I posted a very similar question earlier regarding a problem I was having with and pstricks, and cmhughes helped me a lot. But now, I just want to change the font in the proof environment to a bold red, and I (think) I shall be done fiddling with these darn environments! Thanks cmhughes and everyone else who has been of so much help to me here!!!

Would a start be something like the following (not sure, but I shall take a stab):

\renewenvironment{proof}[1]{proof}{}
\theoremstyle{plain}
\theoremheaderfont{sc}\theorembodyfont{\textcolor{\red[1]{\bfseries}}}
\theoremseparator{}
\theoremsymbol{\rule{1ex}{1ex}}
\newtheorem{proof}{Proof}

I am really not sure if that works at all, but I did want to at least put some effort into this before I 'blindly' asked the question this time. Thanks again. -MD

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  • 2
    Using red for long texts (and proofs often are long) might be tiresome for readers; have you considered another approach? Commented Aug 5, 2013 at 13:16
  • @GonzaloMedina I am not sure. I just want some method to have the body of the proof to stand out in some way that is 'unique' and maybe has never been done. I am certainly open to other suggestions. Perhaps having all of the text in bold-face font on top of a red background? Not sure... Commented Aug 5, 2013 at 13:40

1 Answer 1

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A few comments

  • Post something that actually compiles
  • You never load a package providing color
  • \textcolor takes two arguments, and the text is never given to it. Use \color{...} instead.
  • \sc is not good practice in LaTeX
  • You may want to have a look at mdframed as well, and give better framed theorems.

Besides, there is no need to manually load amstext, amsmath already does.

\theorembodyfont{\color{red}\bfseries\boldmath}

works just fine.

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