2. Open the book whose background color you want to change.

3. Click on the middle of the screen to bring up the menu bar.

4. In the menu bar, find and click the "Show" option.

5. In the display options, there are some options about background and text color. Click the Background option.

6. There will be different color choices, from which you can choose your favorite color as the background.

7. After selection, click on the color and confirm.