%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 11-2-10 on page 728.
%% 
%%  Copyright (C) 2007 Michel Goossens, Frank Mittelbach, Denis Roegel, Sebastian Rahtz, Herbert Vo\ss 
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{87.83385pt}
\setlength\parindent{0pt}
\StartShownPreambleCommands
\usepackage{xcolor}
\providecolorset{gray}{Gray}{}{9,0.9;6,0.6;3,0.3}
\StopShownPreambleCommands
\begin{document}
\newcommand\blob[1]{{\color{#1}\rule{3cm}{5mm}}}
\blob{Gray9}\\ \blob{Gray6}\\ \blob{Gray3}
\end{document}