Changing background color of text in Latex

I know this question has been answered very extensively. But not what I wanted or thought was the question based on the title. Therefore if others get in here looking for a possibility for colouring behind a word than this snippet is much easier:

\colorbox{blue!30}{blue}

or

\textcolor{blue!30}{blue}

resulting in:

This is possible by only adding \usepackage{xcolor}. Just some extra info :)

Colour Several Lines It is correct that the above methods does not work for several lines, if you to be more than one line you can do:

{\color{green} the text you want to write}

This can however also be wrapped in a function so it is easier to use several places during edits, e.g., for colouring new text or whatever:

\newcommand{\added}[1]{{\color{green}[added]:#1}}

I prefer using tcolorbox thinking that in future you may want the background to be fashionable. I have given many options (which are not needed for this particular case) in the tcbset so that you can play with them to suit your needs.

\documentclass{article}
\usepackage[most]{tcolorbox}

\tcbset{
    frame code={}
    center title,
    left=0pt,
    right=0pt,
    top=0pt,
    bottom=0pt,
    colback=gray!70,
    colframe=white,
    width=\dimexpr\textwidth\relax,
    enlarge left by=0mm,
    boxsep=5pt,
    arc=0pt,outer arc=0pt,
    }

\begin{document}
\begin{tcolorbox}
\textsc{Extra Curricular Achievements}
\end{tcolorbox}
\end{document}

Here is another option using framed package.

\documentclass{article}
\usepackage{xcolor}
\usepackage{framed}
\definecolor{shadecolor}{RGB}{180,180,180}
\begin{document}
\begin{snugshade*}
\noindent\textsc{Extra Curricular Achievements}
\end{snugshade*}
\end{document}

Without extra packages:

\documentclass{article}
\usepackage{xcolor}
\definecolor{shadecolor}{RGB}{150,150,150}
\begin{document}
\noindent\colorbox{shadecolor}
{\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\textsc{Extra Curricular Achievements}}}

\end{document}

And convert it in to a macro:

\documentclass{article}
\usepackage{xcolor}
\definecolor{shadecolor}{RGB}{150,150,150}
\newcommand{\mybox}[1]{\par\noindent\colorbox{shadecolor}
{\parbox{\dimexpr\textwidth-2\fboxsep\relax}{#1}}}
\begin{document}
\mybox{\textsc{Extra Curricular Achievements}}

\end{document}

Just to add to the last comment. One can use the `minipage' environment to extend over several lines:

\colorbox{blue!10}{
\begin{minipage}{\textwidth}
\color{RoyalBlue} 

One line.

Another line.

The final line.
\end{minipage}
}