A family of Microsoft word processing software products for creating web, email, and print documents.
Background Color is a document-specific option; it can't even be changed by section as some other options (such as watermarks) can. If you can create the last page as a separate section, you can insert a colored rectangle Behind Text anchored to the page header. If not, you'll have to anchor the shape to a paragraph on the page (the last paragraph would be prudent, as that would make sure the shape stays on the last page).