How to change colors in Beamer theme?

I would like to change colors in Beamer theme like Amsterdam (downloaded from the side http://latex.simon04.net the first topic). How can I get on the top instead of dark blue for example red color and instead of light blue green color? I use the headline defined like this

\setbeamertemplate{headline}
{%
\end{beamercolorbox}
\begin{beamercolorbox}[ht=1.7ex,dp=1.125ex,%
\end{beamercolorbox}%
\ifbeamer@theme@subsection%
\end{beamercolorbox}
\begin{beamercolorbox}[ht=1.7ex,dp=1.125ex,%
\end{beamercolorbox}%
\fi%
\end{beamercolorbox}
} \mode <all>

\makeatletter
\DeclareOptionBeamer{compress}{\beamer@compresstrue}
\ProcessOptionsBeamer

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No offense but the file is 21 lines long. And one of the lines defines the blue. –  percusse Aug 24 '12 at 13:23

\documentclass{beamer}

\mode<presentation>
{
\usetheme{Amsterdam}
\setbeamercolor*{palette secondary}{use=structure,fg=white,bg=red}
\setbeamercolor*{palette tertiary}{use=structure,fg=white,bg=green}
}

\usepackage{lipsum}
\begin{document}
\begin{frame}
\lipsum
\end{frame}

\end{document}


But notice Claudio Fiandrino's comment on the other answer.

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I believe the top panel use the structure foreground color which is defined in

\setbeamercolor{structure}{fg=beamer@blendedblue}


where beamer@blendedblue is a user defined color

\definecolor{beamer@blendedblue}{rgb}{0.137,0.466,0.741}


Simple modify the RGB value to change that. Other colors are imported from

\usecolortheme{whale}
\usecolortheme{orchid}


So you will have to override the definitions in beamercolorthemewhale.sty or beamercolorthemewhale.sty to change them.

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You shouldn't touch the original themes. You can overwrite whatever setting you want to change after loading the theme. –  percusse Aug 24 '12 at 13:32
Besides percusse comment, notice that overriding the structure color template, also affects all palettes. From that point on you should have care to redefine the proper palette to set it in light green as requested. –  Claudio Fiandrino Aug 24 '12 at 13:37