Color is not working properly with XeLaTeX RTL documents?

Question

The following minimal example produced the desired results:

\documentclass{article}
\usepackage[usenames]{color}

\begin{document}
black {\color{red} red} black

black
\end{document}

But the following example, which is just the same, other than the fact it is RTL, does not produce the desired results:

\documentclass{article}
\usepackage[usenames]{color}
\usepackage{polyglossia}
\setmainlanguage{hebrew}
\def \hebrewFont{David CLM}
\setmainfont[Mapping=tex-text]{\hebrewFont}
\newfontfamily{\hebrewfont}{\hebrewFont}

\begin{document}
black {\color{red} red} black

black
\end{document}

Am I doing something wrong, or is it a simple bug?

Answer 1

That is a known e-TeX bug inherited by XeTeX (newer version of the bidi package tries to work around this in some limited cases, but it is not something that can really be fixed with macro code).

Basically what happens is that the TeX--XeT bidirectional TeX extension used by e-TeX reverses TeX’s internal node list when in RTL mode so that things are typeset from right to left. This works fine most of the time, but it breaks when paired \specials are used, like color which is reprsented internally by a pair of \special{color: push …} and \special{color pop}, as this reversal results in the pop special coming before the push one, causing the issue that have been observed.

The next version of XeTeX (0.99992) attempts to fix the root of this issue, but the code is experimental and may or may not actually end up in the released version.