How to set the background color of a template part (Header/Footer) in Twenty Twentythree?

The Twenty Twenty-Three theme comes with an inbuilt “Editor” option that exists under the “Appearance” menu.

Appearance >> Editor

Once you click on the “Editor(beta)” option then you can select the header or footer area and after that, you can customize their stylings like Background Color, Text Color, and Link Color.

The theme also provides many more customization options. You can explore the theme by visiting the below links:

https://wordpress.org/news/2022/11/introducing-twenty-twenty-three/