Change default colors of premade layout

I am working with a non-profit to rebuild their website. They love the placement of all the items in the Design Conference layout pack, but they want to change the default background color across the pack from the blue it uses to black. I have very limited experience working in Divi, and I know how to change the background once a page is created using the layout pack. But is there a way to change the default background color? If I have to create a new layout in my library and use it each time I want to create the page I'm fine with that, but I have no clue what the best way to do this would be. Anyone have suggestions on how to keep everything in a layout pack, but change the background color on it, and then be able to save those templates for later use?

Thank you