DIG A LITTLE DEEPER into FileMaker 13 themes with James Scarpetta (Part 1 here).
In this demo file click on one of the Text styles, make some adjustments like text color and then save the new style by clicking on the Styles Tab in the Inspector and the Icon that is now red next to the style that was updated and you’ll get a dialog like the attached image. If this style is attached anywhere else on this layout when you click Save Changes to Current Style all objects on this layout will update with the updated Style.
There are plenty of styles in each theme that can be added to or modified. Check it the sample file when you get there.