This is actually theme dependant, I ran into issues with it last night
and was able to track it down for the modern theme,
In this directory:
mozilla-win32-talkback\bin\chrome\modern\skin\modern\messenger
in the mailheader.css file there is a section
body {
background-color: white;
}
Kill it to have the background color be the default background color set
in your prefs. Then you have to create a new .zip file from the modern
directory and name it modern.jar replacing the existing modern.jar. If
you still need help lemme know and I should be able to better explain it.
This brings me to my main point, there needs to be alot of testing done
on themes with different default colors set, I went through the Modern
theme and there are lots of places just the foreground or just the
background color are set. This is __bad__. Either all the colors need to
be set or none of them. Where can I report bugs I find in particular themes?