Themes provide a complete slide design for your presentation, including background designs, font styles, colors, and layouts.
Customize your theme
To find a theme to use in your presentation, click the Design tab, click a theme, and see how it previews on the slide.
You can further customize the theme by changing the fonts, colors, and background colors on the Design tab.
To change the fonts and colors, click the down arrow in the Variants gallery, and then click Fonts, Colors, or Background Styles.
For more finely tuned customization, you can edit the slide master.Save your customized theme
On the Design tab, hover over any theme, and click the down arrow button that shows below the themes panel.
Click Save Current Theme.
When you save your theme to the Themes folder, it'll automatically show in the gallery under Custom Themes. If your theme isn't in the Themes folder, click Browse for Themes to look for your theme in its saved location.