\documentclass{article}
\usepackage{%color, % automatically loaded by overprint
  overprint}

% IMPORTANT! Define all colors explicitly as cmyk colors

\definecolor{mg}{cmyk}{0,1,0,0}
\definecolor{cn}{cmyk}{1,0,0,0}
\definecolor{bk}{cmyk}{0,0,0,1}

\begin{document}
\color{bk}

\colorbox{cn}{text}

\colorbox{mg}{\overprint text}

\colorbox{cn}{text}

\end{document}
