\documentclass[a4paper,12pt]{article}
\usepackage[usenames]{color}

\begin{document}
\pagecolor{black} % Background color

\color{white}     % Text color
\definecolor{Cr}{rgb}{.1,.1,1}
\definecolor{Cdr}{rgb}{.1,.8,1}

\definecolor{Cv}{rgb}{.1,1,.1}
\definecolor{Cdv}{rgb}{.8,1,.0}
\definecolor{Ca}{rgb}{1,.1,.1}
\center
$ \color{Cr}  \vec r $

$ $

$ \color{Cdr} \Delta \vec r $

$ $

$ \color{Cv}  \vec v $

$ $

$ \color{Cdv} \Delta \vec v $

$ $

$ \color{Ca}  \vec a $

$ $

${\color{Cv}\vec v} \approx{ {\color{Cdr}\Delta {\vec r}} \over {\Delta t}} $
 
$ $

${\color{Ca} \vec a} \approx {{\color{Cdv} \Delta \vec v}\over{\Delta t}} $
 
$ $

${{\color{Cdv}| \Delta \vec v|}\over{\color{Cv} v}} = {{\color{Cdr}| \Delta \vec r|}\over{\color{Cr}r}} $

$ $
 
${\color{Ca}  a} \approx {{\color{Cdv}| \Delta \vec v|}\over{\Delta t}} =
 {{\color{Cv} v}{\color{Cdr}| \Delta \vec r|}\over{{\color{Cr}r} \Delta t }} 
\approx {{\color{Cv} v}^2 \over {\color{Cr}r}}$
 
$ $

 
${\color{Ca}  a}={{\color{Cv} v}^2 \over {\color{Cr}r}}$
 
$ $



\end{document}
