[XeTeX] Bug with color \specials?

[Akira Kakuto]

> I have confirmed that, in the case of dvipdfmx,
> \documentclass[dvipdfm]{article}
> is ok, but
> \documentclass[dvipdfmx]{article}
> is ng.
> 
> Therefore the bug may be in dvipdfmx.def and xetex.def.

However,
latex --> dvi --> dvipdfmx --> pdf
for

\documentclass[dvipdfmx]{article}
\def\pgfsysdriver{pgfsys-dvipdfm.def}
\usepackage{lipsum}
\usepackage{tcolorbox}
\tcbuselibrary{breakable}
\begin{document}
%
\rule{0.4pt}{17cm}
%
\begin{tcolorbox}[breakable]
\lipsum[1]
\end{tcolorbox}
\lipsum
\end{document}

and xelatex for

\documentclass{article}
\def\pgfsysdriver{pgfsys-dvipdfm.def}
\usepackage{lipsum}
\usepackage{tcolorbox}
\tcbuselibrary{breakable}
\begin{document}
%
\rule{0.4pt}{17cm}
%
\begin{tcolorbox}[breakable]
\lipsum[1]
\end{tcolorbox}
\lipsum
\end{document}

generate good results.
Thus problems are in pgfsys-dvipdfmx.def
and pgfsys-xetex.def.

Best,
Akira