% Code by J Protze
\documentclass{book}
% donothing by paul-pearce
\newcommand{\donothing}[1]{#1}
\newcommand{\ADDdonothing}[1]{{\color{blue}\donothing{#1}}} 
\newcommand{\DELdonothing}[1]{{\color{red}\donothing{#1}}}
\newcommand{\cmd}[1]{#1}
\newcommand{\ADDcmd}[1]{\textcolor{blue}{#1}}
\newcommand{\DELcmd}[1]{\textcolor{red}{#1}}

\usepackage{blindtext}
\newcommand{\DELblindtext}{{\color{red}\blindtext}}
\newcommand{\ADDblindtext}{{\color{blue}\blindtext}}
\newcommand{\mypar}{\paragraph{MYPAR}}
\newcommand{\DELmypar}{\paragraph{\DIFdel{MYPAR}}}
\newcommand{\ADDmypar}{\paragraph{\DIFadd{MYPAR}}}
\begin{document}
\cmd{Test1}
\cmd{Test5}
\end{document}

