Heres a cool way to access the colours setup in the Source Settings such as the Accent, Accent Alt, Secondary, Alt, etc., and apply a colour to be a background colour in a Container. You can use the Custom CSS facility in a Container Base to access teh colour to use for a background.
E.g. To do this for the Secondary colour, you would add the following into the Custom CSS box for say Container Base with ID set to 2, into Background 1:
background-color: var(–second-color);
This sets the BG colour to whatever the Secondary colour is set to in the Source Settings, for every Container that is set to use Base Background 1 with the BG ID set to 2.
The technique is used here at https://www.webdeersign.com/xdemo/v2/ - clicking on any clickable element will take you to another page. The only difference between the 2 pages is that Secondary Colour is light blue in 1 page, and light beige in the 2nd page.
By adding the Source Settings into a Partial used on every page, would make this change across the entire site.