The Blog / Archive > Settings section provides a few settings for customizing the appearance of blog and archive pages.
Currently there is only one color setting here. Other color settings can be found in the other Customizer settings in the Blog / Archive panel.
The background color setting here changes the Body background color on blog and archive pages only. This is useful if you want to have a different background color for archives.
Most of the blog and archive settings are provided by Genesis (the parent theme). They can be found in the Theme Settings > Content Archives section of the Customizer.