Does anyone have any ideas about this? Since the multi-select  box is
a control I can't select any part of it using the IE Developer
Toolbar. And since this is a _layouts directory page, I've even tried
going to the file system page  and overriding it there. No luck
though - no matter what I change, the background  is still that very
dark blue.

I suspect the problem is that's an ActiveX control and probably not
setup to use CSS styles. I doubt you can change  the background  color on
it, no matter what you try.

Just a thought here - this may not work.

The component is an Active X control, and there is no method exposed for
changing the right portion of the window. There is a method for changing the
TreeView portion though.

However, Anna mentioned that she can't read the text when she changes the
body background  color. Therefore, the background color  of the object is
transparent. (I have an intuitive genius for the obvious)

If Anna can find the parent container, probably a <TD> tag, she can change
the CSS for that in the OWS.CSS file to achieve the result she wants. She
will have to modify the upload.aspx file for the Site Definition that she is
using to select the appropriate tag like <TD id="multi'">, and then modify
the CSS file to set #multi td { background-color="white";} or something
close to that. I didn't test the syntax, but hopefully you get the idea.

Obviously the normal caveat to back up the files first applies.