I am editing a LaTeX paper with Emacs. Sometimes I want to make a block of texts less obvious (or less important to see). Instead of totally hiding them, they should still be there. Is there an easy way to embed them in something so that it changes color (to grey for instance)?
By the way, besides changing color, are there other ways to easily make a block of texts look less important?
You can use the xcolor package (which can be installed via tlmgr install xcolor). It provides \textcolor{<color>}{<text>} as well as \color{<color>} to switch the color for some give text or until the end of the group/environment. You can get different shades of gray by using black!x as a color where x is a number from 0 to 100, taken as a percentage with 100 being black.
\usepackage{xcolor}
\begin{document}
This is a sample text in black.
\textcolor{blue}{This is a sample text in blue.}
\end{document}
\textcolor{green}{a couple of words} colors the entire second argument. \color{green} is a declaration, which changes the text color of everything that follows (in that scope, or group as its called in TeX). It is analogous to \textbf versus \bfseries. \color should also work in math mode. But some of the amsmath environments do rather complicated things in order to work (reading the contents several times, for example). But then you could try `{\color{green} \begin{align*} blabla \end{align*} } (note the outer braces).
Commented
May 2, 2011 at 0:40
\color should work in mathmode. It would be best if you give an example so we can see where the problem lies. You could edit your question for this.
Commented
May 2, 2011 at 8:39
The following seems simpler:
\documentclass{amsproc}
\usepackage[colorlinks]{hyperref}
\begin{document}
This is {\color{red} highlighted}, and this is not.
\end{document}
xcolor package is used.
Commented
Sep 6, 2017 at 14:53
\color is not a hyperref command, but that hyperref loads color or xcolor on its own.
All the above answers are excellent for general purpose
If you want to highlight a syntax for a programming language we can use minted package, it provides excellent colored highlighted text.
To use this package you need to have python installed on your system (you can install python using anaconda package it's great choice) in addition to a package called pygments (to install this package use pip install pygments) it's a python library used to highlight programming language syntax
I'll give a simple example of how to use it
\usepackage{minted}
\usemintedstyle{vim} %note here you can use different highlighting
%styles see the final note below
\begin{document}
\begin{minted}{python}
import matplotlib.pyplot as plt
import numpy as np
T=1
delta_T=T/200
alpha=0.5
fc=40/T
A_m=1
t=[i for i in np.arange(-5,5,1/200)]
t_arr=np.array(t)
N=len(t)
g_T=[]
for i in range(N):
if (abs(t[i])!=(T/2*alpha)):
g_T.append(np.sinc(t[i])*(np.cos(np.pi*alpha*t[i]/T)/
(1- 4*alpha**2 *(t[i])**2 /(T**2))))
else:
g_T.append(0)
\end{minted}
\end{document}
This code will produce the following 
Note you need to enable " -shell-escape " option with either LaTeX or pdfLaTeX
latex -shell-escape foo.tex
or
pdflatex -shell-escape foo.tex
If you want to get different highlights, on the command line use
pygmentize -L styles
You'll get different styles of highlighting
CHEERS, Hizzani
Use the package
\usepackage{xcolor}
and right after that write this line given below :
\newcommand{\myRed}[1]{\textcolor{red}{#1}}
Now wherever you want to highlight some text use \myRed{}.
When you compile, you will get text in \myRed in red color.
