color.tex

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
 
\usepackage[dvipsnames]{xcolor}
\colorlet{LightRubineRed}{RubineRed!70!}
\colorlet{Mycolor1}{green!10!orange!90!}
\definecolor{Mycolor2}{HTML}{00F9DE}

\definecolor{matrixcolor}{HTML}{FF0000}
\newcommand{\red}{\textcolor{matrixcolor}}

\begin{document}
 
This document present several examples on how to use the \texttt{color} package 
to change the colour of elements in \LaTeX.

$$ \sum_{\red{foo}}^{bar} x^2 + y^3 $$

\begin{itemize}
\item \textcolor{Mycolor1}{First item}
\item \textcolor{Mycolor2}{Second item}
\item \red{Second item}
\end{itemize}
 
\end{document}