A fast way to give your slides an attractive, professional look in PowerPoint is to apply a theme. Apply a theme to all slides, or specific slides, for a unique impact.
Select Design. Hover over the Themes to preview how it looks, and select the one you like.
Select More to see more Themes.
By default, the theme you select applies to all slides in your presentation.
In the Variants group, select More to change Colors, Fonts, Effects, and Background Styles.
Note: To apply a theme to only one or a few slides, select the slide or slides, right click the theme you want, and select Apply to Selected Slides.