[XeTeX] Bug with color \specials?

[Akira Kakuto]

> latex ---> dvi ---> dvipdfmx ---> pdf
> shows the same drawback:
> 
> \documentclass[dvipdfmx]{article}
> \usepackage{lipsum}
> \usepackage{tcolorbox}
> %
> \tcbuselibrary{breakable}
> %
> \begin{document}
> %
> \rule{0.4pt}{17cm}
> %
> \begin{tcolorbox}[breakable]
> \lipsum[1]
> \end{tcolorbox}
> \lipsum
> \end{document}
> 
> Therefore the bug may be in (x)dvipdfmx.

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.

Best,
Akira