Since you already know how to change the color of lines and to change their thickness, it is time to move on and learn about another option that lets you play with how lines look. In this tutorial, you will learn to apply a dashed style to any line (or shape outline). A dashed style in PowerPoint 2011 can have plenty of variations from fewer dashes to ones with longer or smaller dashes, or even alternating small and long dashes.
Learn how to apply dashed styles to lines (shape outlines) in PowerPoint 2011 for Mac.

