PowerPoint provides four views for working with presentations. You can change between these views using the commands on the VIEW tab in the Presentation Views group:
You may want to change your presentation view from color to grayscale. It is useful to view your presentation in grayscale if you are going to print black and white printouts or if your audience might do so.
To view your presentation in grayscale:
On the VIEW tab, you can set page setup options for your presentation.
From the Zoom group, select Zoom and then in the Zoom dialog box, select a Zoom to option and click OK.