A Google Docs document usually has a white background on each page. If you want to customize the color of the page in Google Docs, you can do so in the page settings menu. See below exactly how it is done.
To get started, open an existing Google Docs document or create a new file for processing. In the open document, click File> Page Setup to access the page settings menu.
In the "Page Setup" box that appears, select a new one Colour for the page by selecting the “Page Color” circular icon.
This will display a drop-down menu showing various preset colors.
Click one of these color options to select it as the color of your page, or select the “+” icon at the bottom (below the “Custom” tab) to create a custom unique color.
In the custom color menu, you can enter a hex color code (for example, # 000000 for black) or use the tool color matching to find the color and shading you want.
Move the Hue bar at the bottom to select the primary or secondary color you want to use, then select a shading using the color matching tool above.
Click "OK" as soon as you find the color you want to use.
Once you have selected the color of your page, select the "OK" button in the "Page Setup" menu to apply in your document.
This will apply the change to all pages of your document.
Unfortunately, it is not possible to apply different colors to each page in a Google Docs document. To achieve the same result, you need to transfer it content in multiple Google Docs files and edit the color of the page for each document separately.