Using this procedure you can highlight important sections and content of your PowerPoint slides. However, you can still add a text box with any desired color to surround text that you want to call out or highlight. Seems Microsoft do not provide an on-screen highlight marker to highlight text. The ability to highlight text in your presentation with color is not available in versions of Microsoft Office PowerPoint after PowerPoint 2007. PowerPoint for Mac let you draw shapes as in Microsoft Windows so you can follow the same procedure described here. In Microsoft Office for Mac you can highlight text in a similar way as you can do in the Windows version of Microsoft Office.

For instance, try to change the shape and use a Cloud Callout shape in PowerPoint instead of the rectangle. If you want the yellow box to look more realistic then you can use a custom shape (you can draw the custom shape yourself or base it in an existing shape). Making the Highlighted Shape Look More Realistic