Until now, section background in modern pages could not be customized…but this is not a problem anymore thanks to the addition of this feature to modern pages in SharePoint Online (SPO) so we can choose the section background experience in the section settings panel:
We can choose between four possible background options. For instance, if we select “Strong”, we will get the following result:
Of course, section background is also linked to the theme used in the site. Therefore, if we change the site theme, the section background color will follow the styles defined in the theme selected.