1. Open the Word document. At this point, the background color in the page is "white". You need to fill the background color with other colors.

2. Then click the "Design" option in the toolbar at the top of the page.

3. Then find the "Page Color" option under the "Design" column.

4. Click the drop-down box under "Page Color" to open the color option and select the color as needed.

5. For example, if you choose "water green", you can change the page of the Word document to water green.