In Author Theme 4.0.0 we began moving the design customizations options to the customizer. (Appearance -> Customizer)
For more advanced customizations you should be using a child theme.
The Customizer settings are split into 9 groups:
Background
Background Color
Header
Logo
Header Position
Navigation
Navigation Position
Background Color
Background Hover Color
Link Color
Link Hover Color
Content
Post Excerpt Length
Hide Number of Comments
Hide Post Author
Hide Post Categories
Hide Publish Date
Hyperlinks
Text Decoration
Hyperlink Color
Hyperlink Hover Color
Buttons
Button Text Color
Button Background Color
Button Background Hover Color
Typography
Logo Font
Navigation Font
Headings Font
Content Font
Logo Color
Headings Color
Content Color
Footer
Footer Divide
Custom Code
Custom CSS Code