preview-1.286; Foreground always black with XeLaTeX

Remember to cover the basics.  Including a minimal LaTeX example
file exhibiting the problem might help.

When TeX-engine set to xelatex, foreground color fixed to black.

Steps to reproduce:

1. Start emacs with -q (Confirmed with both Emacs 24 and 23)

2. M-x set-background-color to black and M-x set-foreground-color
   to white

3. Evaluate these AUCTeX loading configuration:

--8<---------------cut here---------------start------------->8---
(load "auctex.el" nil t t)
(load "preview-latex.el" nil t t)
(setq TeX-engine-alist
      '((xelatex "XeLaTeX" "xetex" "xelatex" "xelatex")))
(add-hook 'LaTeX-mode-hook
          '(lambda ()
             (setq TeX-engine 'xelatex)))
--8<---------------cut here---------------end--------------->8---

4. Find an arbitrary LaTeX document, and C-c C-p C-d.

Also found that if I don't set TeX-engine to xelatex as above,
color is fine.  And I tried using the builtin 'xetex engine,
foreground color is also black.