# Where can I find beamercolorbox options defined?

I am trying to understand the \begin{beamercolorbox}[wd=\paperwidth,ht=2.5ex,dp=1.125ex]{palette quaternary} line. I would like to know where it is defined the palette quaternary and if there are other options? Where can I learn about sty?

\documentclass[final]{beamer}
\mode<presentation> {
% \usetheme{Berlin}
% \usetheme{Rochester}
\usetheme{Copenhagen}
}
\usepackage[english]{babel}
\usepackage[latin1]{inputenc}
\usepackage{amsmath,amsthm, amssymb, latexsym}
\usepackage{booktabs}
\usepackage{xcolor}
\usepackage{tcolorbox}
\usepackage[orientation=landscape,size=a4,scale=1.2,debug]{beamerposter}

% colors
\setbeamercolor{block body}{fg=black,bg=white}

% beamer template
\leavevmode%
\hbox{%
\begin{beamercolorbox}[wd=\paperwidth,ht=2.5ex,dp=1.125ex]{palette quaternary}%
\end{beamercolorbox}%
}


The palette quaternary is defined as \setbeamercolor*{palette quaternary}{fg=white,bg=black} in beamercolorthemewhale.sty, this is one of the colour themes called by the Copenhagen theme.

But you can basically use any beamer colour you like.

\documentclass[dvipsnames]{beamer}

\usetheme{Copenhagen}

\setbeamercolor{mycolor}{fg=RoyalBlue,bg=GreenYellow}

\begin{document}

\begin{frame}
\begin{beamercolorbox}[wd=\paperwidth,ht=2.5ex,dp=1.125ex]{mycolor}%
colored text
\end{beamercolorbox}%
\end{frame}

\end{document}