Remove or change the current theme

1. On the Design tab, in the Themes group, click the More button (illustrated below) to open the entire gallery of themes:

   

2. Do one of the following:

   • To apply a built-in theme, under Office or Built-In, click the theme that you want.

   • To apply a newly-created theme or an existing theme that you previously modified and saved, under Custom, click the theme that you want.

   • To apply a custom theme or a themed document stored in a different location, click Browse for Themes, and then locate and select the theme you want.

To remove a colorful theme, apply the Office Theme for a simple design with a plain white background.

1. On the Design tab, in the Themes group, click the More button (illustrated below) to open the entire gallery of themes:

   

2. Under Office or Built-in, locate and click the Office Theme, which has a white background.

   

See Create your own theme in PowerPoint.

Let's say you have a bunch of slides borrowed from different sources and they don't match visually. You can unify the look of the slides in a few clicks:

1. In the slide thumbnail pane on the left, select a slide.

2. On the Design tab, in the Themes group, click the More button (illustrated below) to open the entire gallery of themes:

   

3. Point the mouse at the theme you want to apply. Right-click it, and then select Apply to All Slides.

   

   If you change your mind, you can undo immediately by pressing Alt+Backspace, or you can repeat step 3 with a different theme.

1. In the slide thumbnail pane on the left, select the slide or slides that you want to apply a theme to.

   (To select multiple slides, press and hold the Ctrl key while you click the individual slides.)

2. On the Design tab, in the Themes group, click the More button (illustrated below) to open the entire gallery of themes:

   

3. Point the mouse at the theme you want to apply. Right-click it, and then select Apply to Selected Slides.

   If you change your mind, you can undo immediately by pressing Alt+Backspace, or you can repeat step 3 with a different theme.

1. Select File > New.

2. Select Blank Presentation.

   A presentation with a white background opens.