Recolor text, such that floats and footnotes are affected correctly

Question

I want to define an environment redout, that causes all text defined inside to be typeset in a changed color. However, I can't find a way to consistently recolor floats.

• If recoloring is performed with just \color{red}, it doesn't affect floats and footnotes, and depending on the document class, may not affect headings either.
• When adding \let\default@color\current@color, it affects floats and footnotes wrongly based on when they are typeset, rather than when they are defined.

I can imagine making this work by redefining all footnote/float commands, but that is error-prone. Is there any more elegant version to achieve coloring based on the position in the source-code?

                      

\documentclass{article}
\usepackage[paperwidth=8cm,paperheight=3cm,scale=0.9]{geometry}
\usepackage{xcolor}

\begin{document}

This text is black.
\footnote{This footnote should be black, but is red.}

\begingroup
\color{red}
\makeatletter
\let\default@color\current@color % required to affect footnotes.
This text is red.
\footnote{This footnote is red, as intended.}

\clearpage
This text is still red.
\footnote{This footnote should be red, but being \emph{typeset} after the \texttt{\string\endgroup}, it isn't.}
\endgroup

This text is correctly black again.
\end{document}

Answer 1

As you show redefining \default@color does more harm than good, I think if you want to set footnotes in the current colour it is simpler just to set the colour at the start of the footnote either explicitly as here or by redefining \footnotetext macro to add the colour \color{.}.

\documentclass{article}
\usepackage[paperwidth=8cm,paperheight=3cm,scale=0.9]{geometry}
\usepackage{xcolor}

\begin{document}

This text is black.
\footnote{\color{.}This footnote should be black, but is red.}

\begingroup
\color{red}

This text is red.
\footnote{\color{.}This footnote is red, as intended.}

\clearpage
This text is still red.
\footnote{\color{.}This footnote should be red, but being \emph{typeset} after the \texttt{\string\endgroup}, it isn't.}
\endgroup

This text is correctly black again.
\end{document}

Answer 2

With lualatex or xelatex you could use colored fonts. That's quite reliable, but math must be reset at the end of the group:

\documentclass{scrartcl}
\usepackage[paperwidth=8cm,paperheight=3cm,scale=0.9]{geometry}
\usepackage{fontspec,unicode-math,xcolor}

\setmainfont{Latin Modern Roman}
\setsansfont{Latin Modern Sans}

\begin{document}

This text is black.
\footnote{This footnote should be black}
\[a=\int x\]

\begingroup
\setmainfont{Latin Modern Roman}[Color=FF0000]
\setsansfont{Latin Modern Sans}[Color=FF0000]
\setmonofont{Latin Modern Mono}[Color=FF0000]
\setmathfont{Latin Modern Math}[Color=FF0000]
\section{should be red}
This text is red. \[a=\int x\]
\footnote{This footnote is red, as intended.}

\clearpage
This text is still red. \textcolor{green}{even with color green ...} unless you use
{\addfontfeature{Colour=green} addfontfeature}
\footnote{This footnote should be red, even after the \texttt{\string\endgroup} $a=\int x$.}

\begin{figure}[t]
This float should be red
\[a=\int x\]
\end{figure}
\endgroup \setmathfont{Latin Modern Math}

This text is correctly black again. \[a=\int x\]
\end{document}