I have noticed a weird vertical spacing issue when combining \color with an enumerate environment. Basically, it seems that {(line break)} takes up different amounts of horizontal space depending on how it is wrapped in \color and extra {...}, leading to extra lines being allocated (vertical space):
\documentclass{article}
\usepackage{color}
\newcommand{\red}[1]{{\color{red}{#1}}}
\newcommand{\var}[1]{\color{red}{#1}}
\begin{document}
\begin{enumerate}
\item \hspace*{320pt}\red{
}
\end{enumerate}
This line is way too far down!
\begin{enumerate}
\item \hspace*{320pt}{\color{red}{
}}
\end{enumerate}
Same here! But compare to the next ones:
\begin{enumerate}
\item \hspace*{318pt}\red{
}
\end{enumerate}
Less hspace - not as far down (interestingly: overfull hbox!)
\begin{enumerate}
\item \hspace*{320pt}\var{
}
\end{enumerate}
One less level of curly braces - not as far down
\begin{enumerate}
\item \hspace*{320pt}\red{%
}
\end{enumerate}
Line break commented - not as far down
\begin{enumerate}
\item \hspace*{320pt}\red{}
\end{enumerate}
No line break in colored text - not as far down
\begin{enumerate}
\item \hspace*{320pt}{{
}}
\end{enumerate}
No color - not as far down
\begin{enumerate}
\item \hspace*{320pt}
\end{enumerate}
Standard case - not as far down
\end{document}
To be honest, I don't really know what my question is: I have encountered this as a result of latexdiff (which introduces extra line breaks at the end of \DIFadd constructions - hence the tag), but it's really only relevant at the end of very full lines, and easy to miss. I have solved this by shortening the sentence (yes, I did), so I think the most relevant question is, why is that? Is there anything on a general level that I can do against that?
