How to find the names of the panels in a beamer color theme and change their colors?

Question

The Beamer manual (17.2.3 Setting Beamer’s Colors) shows how to set colors of specific parts of the color theme using \setbeamercolor. However, since many different color themes have different named parts, how can one find out the name of the part (panel for example) in order to change its color?

For example:

\documentclass[xcolor=dvipsnames]{beamer}

\title[XYZ]{Xblah Yblah Zblah}
\author{Prof Smarty Pantsson}

\date{End.Of.TheWorld,\\Base, Moon} 

\usetheme{PaloAlto}
\usecolortheme{seahorse}
\useinnertheme{rectangles}

\definecolor{logoBlue}{HTML}{003278}
\definecolor{blueDark}{HTML}{a3b6d4}
\definecolor{blueLight}{HTML}{e7eef8}
\definecolor{grey}{HTML}{b1b5b8}

\setbeamercolor*{palette tertiary}{bg=blueDark}
\setbeamercolor{frametitle}{fg=black,bg=blueLight}
\setbeamercolor{normal text}{fg=black,bg=white}

\usefonttheme{serif}

\begin{document}

\frame{\titlepage}

\begin{frame}
  \frametitle{Frame title}

  \begin{itemize}
    \item Text Text Text Text Text Text
    \item Text Text Text Text Text Text
  \end{itemize}
\end{frame}

\end{document}

this changes the title panel of the seahorse color theme:

However, I can't find the names of the other panels (side panel and the square in the upper left corner) in the Beamer manual.

What are the names of the other panels in the seahorse color theme?

How can I find the similar names in any beamer color theme?

Answer 1

Try & error

If one has no clue what the name of a specific colour is, there are some likely colours which are worth a try. You found the first one yourself, the palette tertiary. Besides this colour also try palette secondary and palette primary. These three colours define most elements of a colour theme.

Finding likely names

But for some things one just has to give the correct name, e.g. for the sidebar. To find out possible names to try until one finds the correct name, I recommend http://www.cpt.univ-mrs.fr/~masson/latex/Beamer-appearance-cheat-sheet.pdf which nicely summarises the most important names.

Never forget

To also change the colour structure. Basically all colours of the theme are based on various shades of this colour. If you change this one as well, you are save to not having forget any colour to change. (You blueDark seems not dark enough to use it for elements like bullet points, so I mixed a bit black into it)

\documentclass[xcolor=dvipsnames]{beamer}

\title[XYZ]{Xblah Yblah Zblah}
\author{Prof Smarty Pantsson}

\date{End.Of.TheWorld,\\Base, Moon} 

\usetheme{PaloAlto}
\usecolortheme{seahorse}
\useinnertheme{rectangles}

\definecolor{logoBlue}{HTML}{003278}
\definecolor{blueDark}{HTML}{a3b6d4}
\definecolor{blueLight}{HTML}{e7eef8}
\definecolor{grey}{HTML}{b1b5b8}

\setbeamercolor*{palette tertiary}{bg=blueDark}
\setbeamercolor{frametitle}{fg=black,bg=blueLight}
\setbeamercolor{normal text}{fg=black,bg=white}

\setbeamercolor*{palette primary}{bg=blueDark}
\setbeamercolor*{palette secondary}{bg=blueDark}
\setbeamercolor*{sidebar}{bg=blueLight}
\setbeamercolor*{structure}{fg=blueDark!60!black}

\usefonttheme{serif}

\begin{document}

\frame{\titlepage}

\begin{frame}
  \frametitle{Frame title}

  \begin{itemize}
    \item Text Text Text Text Text Text
    \item Text Text Text Text Text Text
  \end{itemize}
\end{frame}

\end{document}