Set a master screen:
First, you have to create a master screen. This contains, for instance, a navigation bar that should be shared with all other screens. Once it is created, you can create a new screen and place it on the canvas. After selecting the screen, you can select the master screen in the "Master Screen" section by clicking on Add Master Screen. Now, all elements from the master screen are copied to the child screen.
Extend the master screen:
When you want to change the style of an element that is copied from a master screen, you have to explicitly enable editing. Select the element, and click Enable Editing. In the properties panel on the right side, you have to enable editing. Once editing is enabled, you can change the font color to give a visual indication.