[Tex/LaTex] Change text color of section title in \sectionpage

beamerpandoctemplates

I write beamer lecture slides in R Markdown and I want to make a simple style that matches my college's PowerPoint templates, but I am getting caught up on how to change text color in section pages. R Markdown uses Pandoc, which turns all sections above the slide level into section pages (I'll give the code below). So, say I set the slide level at 3, subsubsections will become slides and section and subsection headings will become section and subsection pages. I am making a style file so that I can avoid fidgeting with every file, one-by-one.

Everything I do with \setbeamercolor leaves the section pages with blue text. I am happy to make all text black, or a mix of green and black (I set all other blue items to green), I just don't want any blue text.

How can I make text on section pages green?

Here is a MWE, including the bit that generates section pages. [Now my MWE includes the title page on the second page, too, but I can sort that out later, that doesn't happen in my larger files.]

\documentclass{beamer}

\usetheme{Babson}

\AtBeginSection{
\let\insertsectionnumber\relax
\let\sectionname\relax
\frame{\sectionpage}
}

\title{Test}
\author{W.T. Door}
\date{}

\begin{document}

\titlepage

\section{Test}

\begin{frame}{Test}
Test
\end{frame}

\end{document}


Here and here are my style files. I put the text color changes in the inner file.

theme file:

\ProvidesPackage{beamerthemeBabson}[]

\definecolor{babsonGreen}{HTML}{016F4A}

\useoutertheme{Babson}
\useinnertheme{Babson}

\usepackage{tikz}
\usepackage{MWE}


outer theme:

\ProvidesPackage{outerthemeBabson}[]

% green first page, white with logo otherwise
\setbeamertemplate{background canvas}{
\includegraphics[width=\paperwidth,height=\paperheight]{example-image-a}
\else
\begin{tikzpicture}[remember picture, overlay]
\node [xshift=-0.15\textwidth, yshift=0.15\textheight] at (current page.south east)
{\includegraphics[width=0.15\textwidth]{example-image-b}};
\end{tikzpicture}
\fi
}

% green frame title
\setbeamercolor{frametitle}{bg=babsonGreen, fg=white}


inner theme:

\ProvidesPackage{innerthemeBabson}[]

\setbeamercolor{author}{fg=white}
\setbeamercolor{title}{fg=white}
\setbeamercolor{date}{fg=white}

\setbeamercolor{item}{fg=babsonGreen}
\setbeamercolor{enumerate}{fg=babsonGreen}

\setbeamercolor{block title}{fg=babsonGreen}
\setbeamercolor{sectionpage title}{fg=babsonGreen, bg=babsonGreen}


To change the textcolor of the section on the \AtBeginSection-slides, you need to change the color of "part title", so use \setbeamercolor{part title}{fg=babsonGreen}, for example. To find it, I looked in beamerinnerthemedefault.sty, everything you don't specify is specified in the default files.

The relevant definition is:

\defbeamertemplate*{section page}{default}[1][]
{
\begingroup
\centering
{\usebeamerfont{section name}\usebeamercolor[fg]{section name}\sectionname~\insertsectionnumber}
\vskip1em\par
\begin{beamercolorbox}[sep=12pt,center,#1]{part title}
\usebeamerfont{section title}\insertsection\par
\end{beamercolorbox}
\endgroup
}


Where the beamercolorbox called part title is used.