How to change the shaded color of the \rule{…}{…} command?

Question

To change the shaded color of the \rule{...}{...} command, one solution is

\textcolor‎{‎blue‎}{\rule{2cm}{2cm}}‎

but I want to know how can I directly change the color of this command globally?

Answer 1

You could do

\makeatletter
\let\old@rule\@rule
\def\@rule[#1]#2#3{\textcolor{blue}{\old@rule[#1]{#2}{#3}}}
\makeatother

But it may be better to instead define a new \colorrule command and use that instead, as you may find \rule is used in unexpected places so if you redefine it you may be changing more than you want to change.

---

If you need to override this sometimes it's probably better to use a colour such as rulecolor rather than blue that you can (re)define when needed:

\documentclass{article}

\usepackage[dvipsnames]{color}

\makeatletter
\let\old@rule\@rule
\def\@rule[#1]#2#3{\textcolor{rulecolor}{\old@rule[#1]{#2}{#3}}}
\makeatother

\definecolor{rulecolor}{named}{Blue}

\usepackage{color}

\begin{document}

\rule{1cm}{1cm}

\bigskip

\rule{.1cm}{1cm}

\bigskip

{\definecolor{rulecolor}{named}{Red}\rule{1cm}{1cm}}

\bigskip

\rule{1cm}{1cm}


\end{document}

Answer 2

I just do the following on a case by case basis.

\textcolor{blue}{\rule{2cm}{2cm}}

But if you want to define your own command, you can put this in the preamble or latter.

\newcommand{\myRule}[3]{
    \textcolor{#1}{\rule{#2}{#3}}
}

And if you want to fix the color, try:

\newcommand{\myRule}[3]{
    \textcolor{red}{\rule{#2}{#3}} %change red to blue, green black whatever.
}