[AUCTeX] The color of equations generated by preview-latex doesn't match my emacs color settings

[Wei Zhang]

I first tried to use the default settings, my emacs uses bg:gray12 and fg:gray66,
but the equations generated are white over blue, which looks like this:

http://att.newsmth.net/att.php?p.573.87590.582.png 

Then I tried to change the settings in "Preview Reference Face" to 

Preview Reference Face:(sample) Hide Face
   State: SET for current session only.
   Face consulted for colors and scale of active previews. More
Choice: Value Menu 
 Attributes: [ ] Font Family: *
             [ ] Font Foundry: *
             [ ] Width: *
             [ ] Height: *
             [ ] Weight: *
             [ ] Slant: *
             [ ] Underline: *
             [ ] Overline: *
             [ ] Strike-through: *
             [ ] Box around text: *
             [ ] Inverse-video: *
             [X] Foreground: red        (sample)
             [X] Background: yellow     (sample)
             [ ] Stipple: *
             [ ] Inherit: *

and I end up with weird colored equations like this:

http://att.newsmth.net/att.php?p.573.87590.527118.png

I think the colors for equations should conform to settings in "Preview Reference Face"? 

Did I miss something?

Thanks