1, first of all, open the cell phone installed in the PPT production applications, for example, open the WPS office in the PPT, you can see that at this time the background is the default white.

2, click the icon in the lower left corner of the page, the picture is the settings button.

3, and then in the open settings page, click on the "View" option, and select the "Slide Background" option.

4, and then in the open background settings page as needed to select a solid color background or add a picture background.

5 If you choose a solid blue background and select Apply to all slides, you can add a blue background to all pages.