Background Color Obscures Contents in PDF

[Jona Steenbrink]

Hi .

First time poster, long-time reader...

FM 8.0p266 (unstructured) on Windows XP (actually on MacBook running  
Parallels, but I don't think that's relevant).

My problem is this:
I have pages that contain large diagrams, and I want to differentiate  
them from the regular text pages by adding a background color to the  
page, making them visually clearly distinct from the facing pages.
To this end, I've inserted a floating anchored frame containing  
screenshots, callouts, etc., then drawn an 8.5x11 colored rectangle on  
the page, "sent it to back", and voila! But not so fast. When I save  
the entire document to pdf, all that appears on the large diagram page  
is the colored rectangle: no diagrams. If, however, I save a single  
large diagram page to pdf, it appears as I want it to.
I have also tried creating a new master page with a background color  
and assigning that master page to the page with the diagram, but the  
results are the same as described above when saved as pdf
It also doesn't appear to matter if I select overprint or knockout in  
the object or color properties.

Does anyone have any suggestions on why "save to pdf" is behaving like  
this? Are there any settings I can change.
Alternatively, if someone can tell me the correct way to accomplish  
what I am trying here, I would be immensely grateful.

Thanks in advance,

Jona Steenbrink