Comportamento estranho com alerta no modo matemático

Question

Recebi esse comportamento inesperado quando mudo a cor para alerted textin mathmode. Em particular, alerted text.fgparece mudar apenas quando \alerté chamado novamente. Mudar com \colorletafeta apenas a cor interna mathmode.

Aqui um exemplo

\documentclass{beamer}
\begin{document}    
\begin{frame}{Title}
    $\begingroup\setbeamercolor{alerted text}{fg=blue}\alert{blue}\endgroup+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
    
    $\begingroup\setbeamercolor{alerted text}{fg=blue}\alert{blue}\endgroup\setbeamercolor{alerted text}{fg=red}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
    
    $\begingroup\setbeamercolor{alerted text}{fg=blue}\alert{blue}\endgroup\setbeamercolor{alerted text}{fg=red}\colorlet{alerted text.fg}{red}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
    
    $\begingroup\setbeamercolor{alerted text}{fg=blue}\alert{blue}\endgroup\setbeamercolor{alerted text}{fg=red}\alert{}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
\end{frame}

\end{document}

Answer 1

\setbeamercolor{}{}em si ainda não cria as cores .fge .bg, elas só são criadas quando a cor do projetor é usada.

Mas, em vez de alterar a cor do alerta para frente e para trás, você pode criar mais macros semelhantes a alertas com a cor que desejar - ou simplesmente usar \structure, que é azul por padrão.

\documentclass{beamer}

\setbeamercolor{foo}{fg=green}

\newenvironment<>{fooenv}{\begin{altenv}#1%
    {\usebeamercolor[fg]{foo}\usebeamerfont{foo}\usebeamertemplate{foo text begin}}
    {\usebeamertemplate{foo text end}}{\color{.}}{}\ignorespaces}{\ifhmode\unskip\fi\end{altenv}}

\newcommand<>{\foo}[1]{\begin{fooenv}#2\relax#1\end{fooenv}}


\begin{document}    
\begin{frame}{Title}
    $\structure{blue}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}
    
    $\foo{green}+\textcolor{alerted text.fg}{red}$  These should be \textcolor{alerted text.fg}{red}, \alert{red} and \textcolor{alerted text.fg}{red}    

\end{frame}

\end{document}