For those that work with orchestra or any music that requires parts to be produced, you may want the bar (measure) numbers in the parts to look different than the numbers in the score. I take a look at that issue in a YouTube tutorial video. I also talk about how to make a special staff on which to display the numbers.
The main sections to look at in Sibelius are the Appearance->Engraving Rules->Bar Numbers and in the Parts tab, part appearance.