Answer:
On the Design tab, select Format Background. Select Solid Fill, and pick a color from the gallery. If you want to have all slides have this same background color, on the Design tab, select Format Background > Apply to All.
Step-by-step explanation:
A template is a predesigned presentation you can use to create a new slide show quickly. Templates often include custom formatting and designs, so they can save you a lot of time and effort when starting a new project.