Please follow to following process to change the background color of :-

Header site title

Goto admin menu >> appearance >> customizer >> typography >> Header site title

Header description

Goto admin menu >> appearance >> customizer >> typography >> Header tagline

Menu

Goto admin menu >> appearance >> customizer >> typography >> Menu

Section title of all section

Goto admin menu >> appearance >> customizer >> typography >> Section title

Post title of all section

Goto admin menu >> appearance >> customizer >> typography >> Post title

Date, no of comment and tag of blog post section

Goto admin menu >> appearance >> customizer >> typography >> Date, comment and tag

Paragraph of page detail / post detail and excerpt of banner / blog post

Goto admin menu >> appearance >> customizer >> typography >> Paragraph / Excerpt

Blockquote of sidebar , inside page / post detail

Goto admin menu >> appearance >> customizer >> typography >> Blockquote

Widget title

Goto admin menu >> appearance >> customizer >> typography >> Widget title

Widget list or widget detail

Goto admin menu >> appearance >> customizer >> typography >> Widget list

Category of banner, feature and blog post section

Goto admin menu >> appearance >> customizer >> typography >> Category

Read more and nave link that shows page number

Goto admin menu >> appearance >> customizer >> typography >> Read more and navLinks