Default Color

I need a way to restore the default color after changing it. One may not know the default color conveniently since it comes from CSS.

In LaTeX, we can restore the default color by doing something like:

\colorlet{colordefl}{.} %save current color
\color{red}
%color is red here
\color{colordefl}
%color is default again

However, \colorlet does not seem to be supported in MathJax. The workaround in most cases is to scope any color changes:

% color is default here
{\color{red}
%color is red here
}
% color is default here again

However, this isn't possible for certain constructs. For example, to color an underbrace and its label, but not its contents:

{\color{red}\
underbrace{\color{colordefl} ...}_{...}
}

This is somewhere between a bug report (\colorlet is missing), a feature request (add it, or equivalent mechanism, please), and a question (how do I do this / is there a workaround?).

The issue names no files or tests; start by tracing MathJax's handling of \color and how LaTeX color macros are supported. Done means providing a documented mechanism to restore the CSS-derived default color where simple scoping is insufficient.