You can choose any background color of your choice. The default background is white.
Choose "Design" category and click
tool button ,and then click the color that you want. To change to a color that is
not in the theme colors (theme colors: A set of colors that is used in a file),
click "More Colors", and then either click the color that you want
on the Standard tab, or mix your own color on the Custom tab.
Tip: If you don't see the background color you chose, it may be because of the presence of other shapes or images.