In PPT, the specific steps of changing white characters on a black background into black characters on a white background are as follows:

The materials we need to prepare are: computer and PPT slides.

1. First, we open the PPT slide to be edited, and click "Background Format" at the back of the design.

2. Then, we click and select "White" in the pop-up window.

3. Then we can see that the white characters on the black background in PPT slides have been changed to black characters on the white background.