[pstricks] exclamation mark

[Herbert Voss]

Doris Wagner wrote:
> sometimes in pstricks-code there are expressions like this:
>
> linecolor=gray!20
>
> I guess that the exclamation mark is something postscript-specific. Can 
> anyone explain the meaning of this exclamation mark or tell me where I 
> can find something about it in the web?
>   
in the PSTricks book pages 15ff or in the documentation of xcolor

\documentclass{article}
\usepackage{xcolor,array}
\begin{document}

\begin{tabular}{@{}*{5}{>{\ttfamily}l}@{}}
\rmfamily\emph{Color expression}
    & \multicolumn{3}{c}{\rmfamily\emph{RGB-Tripel}}\\\hline
\colorbox{red}{red} & 1 & 0 & 0 \\
\colorbox{red!55}{red!75} & 1 & 0.25 & 0.25\\
\colorbox{red!55!blue!100}{\color{white}red!75!blue!100}
    & 0.75 & 0 & 0.25\\
\colorbox{red!55!blue!30}{red!75!blue!405} & 0.9 & 0.6 & 0.7\\
\colorbox{red!55!blue!30!yellow!50}{red!75!blue!40!yellow!50}
    & 0.95 & 0.8 & 0.55\\\hline
%
\colorbox{-red}{-red} & 0 & 1 & 1 \\
\colorbox{-red!55}{-red!75} &  0 & 0.75 & 0.75\\
\colorbox{-red!55!blue!100}{-red!75!blue!100} & 0.25 & 1 & 0.75\\
\colorbox{-red!55!blue!30}{%
  \color{white}-red!75!blue!40} & 0.1 & 0.4 & 0.3\\
\colorbox{-red!55!blue!30!yellow!50}{%
  \color{white}-red!75!blue!40!yellow!50} & 0.05 & 0.2 & 0.45
\end{tabular}
\end{document}


it has nothing to do with PostScript,
-red!55!blue!100
is the complementary color (-) of 55% red with 100% blue

Herbert