Too long for a comment.
The second answer in that thread is a working example.
If you want to change the color when using the soul package you can use the command \setstcolor:
\documentclass{article}
\usepackage{soul,xcolor}
\begin{document}
\setstcolor{red}
\st{Some overstruck text}
\end{document}

The ulem package does not support coloring directly, but looking at its manual, you can find that it is possible to define a new command like
\newcommand\redsout{\bgroup\markoverwith{\textcolor{red}{\rule[0.5ex]{2pt}{0.4pt}}}\ULon}
so that
\documentclass{article}
\usepackage[normalem]{ulem}
\usepackage{xcolor}
\begin{document}
\newcommand\redsout{\bgroup\markoverwith{\textcolor{red}{\rule[0.5ex]{2pt}{0.4pt}}}\ULon}
\redsout{Some overstruck text}
\end{document}
produces the same result as the above one.
soulversion shown above. Maybe the example should call it "understruck" text. – Matt Jan 28 '22 at 16:38