# Change bullet color in TOC for current section only

In my TOC I would like to highlight the current section using a different color. Following the answers to this question, I have managed to change the text color of the current section using

\setbeamercolor{section in toc}{fg=alerted text.fg, fg = red}


Now I also want to change the bullet color of the current section, but so far I've only managed to change to color of all the bullets in the TOC. How can I change the color of the current section bullet in the TOC?

Here's a MWE:

documentclass[xcolor=dvipsnames]{beamer}
\usecolortheme{dolphin}
\useinnertheme{rectangles} % adds squared bullets to TOC

% Define colors of our university
\definecolor{UniGreen}{RGB}{ 0,139,0}
\definecolor{TitleGreen}{RGB}{0,120,0}
\setbeamercolor{title}{fg=TitleGreen}
\setbeamercolor{structure}{fg=UniGreen}
\setbeamercolor{item projected}{bg=UniGreen, fg=white} %define color of the item-bullets
\setbeamercolor{button}{bg=UniGreen}

\AtBeginSection[]
{
\setbeamercolor{section in toc}{fg=alerted text.fg, fg = red} % this changes name of current section to red as desired
\setbeamercolor{section number projected}{fg=alerted, bg=red,fg=white} % THIS LINE OF CODE CHANGES ALL THE BULLETS IN THE TOC TO RED
}

\begin{document}
\section{Test section one}
\begin{frame} test \end{frame}
\section{Test section two}
\begin{frame} test \end{frame}

\frame{\frametitle{Outline}\tableofcontents[currentsection, currentsubsection, subsectionstyle = show, subsubsectionstyle=show]
}

\section{Test section three}
\begin{frame} test \end{frame}
\section{Test section four}
\begin{frame} test \end{frame}

\end{document}