I'm trying to replicate an Excel spreadsheet that someone sent me and I can't figure out how. The print area is set, and all cells outside the print area are greyed out. The cells aren't simply shaded, because Excel says they have no fill, and they aren't hidden/locked/protected because I can still edit them just like normal cells. The only difference is that they're greyed out and the print area has a thick blue border around it. This spreadsheet doesn't have any macros, either.
What feature of Excel is this using?