An easy way to do this is to define a character style (not a paragraph style) that has the style changes that you want for the numbering. Then, select the paragraph mark at the end of the appropriate list paragraph, and apply the style to it. Or, if you just need one number changed in the whole document, select the paragraph mark, and manually apply the style changes to it. Either way, you end up with something like this.
To clear the style from an item, select the paragraph mark, and press Ctrl+Spacebar (or click Clear All in the Styles pane or Clear All Formatting on the Home tab), as usual.