A couple of things to check.
- Tools > Options > LibreOffice > Application Colours > General, Document background. This will select the background colour appearing on-screen.
Oddly, on my Windows 7/LO 5.4 PC, though “Print Preview” still shows the background colour set it does not print,. But it still helps those nostalgic for dear old Wordperfect for DOS’s blue screen or who just don’t like a brilliant white screen.
- In Writer, at least, Format > Page > Area tab lets you set a background colour for the text area, but not the borders, and this will print. I haven’t tried how the other LO applications are affected.