Change color of list bullet in blocks

Question

I want the list bullets in alerted blocks to be red and the otherwise in blue. The problem is that I don't manage to get the right colours.

Here is what comes before

\documentclass[t]{beamer}
\usepackage{xcolor}
\definecolor{red}{HTML}{DC322F}
\definecolor{blue}{HTML}{268BD2}
\colorlet{bullet-list-color}{blue}
\colorlet{alert-list-color}{red}
\colorlet{block-headings-color}{blue}
\colorlet{alert-headings-color}{red}

And the test frame

\begin{frame}
\begin{alertblock}{Alert}
\begin{description}
\item[Alert 1] some explanations.
\item[Alert 2] some explanations.
\end{description}
\end{alertblock}

\begin{block}{Block}
\begin{description}
\item[Block 1] some explanations.
\item[Block 1] some explanations.
\end{description}
\end{block}
\end{frame}

If I add

\setbeamercolor{description item}{fg=bullet-list-color}
\setbeamercolor{description item alerted}{fg=alert-list-color}

I obtain this because the first selector takes precedence over the second.

If I modify it as

\setbeamercolor{normal description item}{fg=bullet-list-color}
\setbeamercolor{description item alerted}{fg=alert-list-color}

now the block list is not selected any more.

I tried to correct it with

\setbeamercolor{normal description item}{fg=bullet-list-color}
\setbeamercolor{description item block}{fg=bullet-list-color}
\setbeamercolor{description item alerted}{fg=alert-list-color}

without success.

Can someone please tell me how to modify the colour of the list inside the block?

Answer 1

\documentclass[t]{beamer}
\definecolor{red}{HTML}{FC322F}
\definecolor{blue}{HTML}{268BD2}
\colorlet{bullet-list-color}{blue}
\colorlet{alert-list-color}{red}
\colorlet{block-headings-color}{blue}
\colorlet{alert-headings-color}{red}

\setbeamercolor{description item}{fg=bullet-list-color}

\usepackage{etoolbox}

\AtBeginEnvironment{alertblock}{%
    \setbeamercolor{description item}{fg=alert-list-color}  
}

\setbeamercolor{block title}{fg=block-headings-color}
\setbeamercolor{block title alerted}{fg=alert-headings-color}

\begin{document}

\begin{frame}
\begin{alertblock}{Alert}
\begin{description}
\item[Alert 1] some explanations.
\item[Alert 2] some explanations.
\end{description}
\end{alertblock}

\begin{block}{Block}
\begin{description}
\item[Block 1] some explanations.
\item[Block 1] some explanations.
\end{description}
\end{block}
\end{frame}
\end{document}