Because style sets go along with themes, whenever you choose a new theme, you get new styles sets to go along with it. The various style sets give you options about the way your headings look, the types of graphic elements used (borders, boxes, and lines, for example), and the way color is assigned to elements and text on the page.
On the Design tab, in the Document Formatting group, review the style sets.
Click More to see additional style sets.
Click the style set you want to apply.
If you would like, modify the set by changing other settings in the Document Formatting group.
Click Save As A New Style Set.
In the dialog box that opens, enter a file name for the new style set. ...