From Theme Options -> Design -> Header Design & Colors tab you can change colors, login modal options, menu font size and hover menu design options

These are settings you can manage.

Login/Register Modal Image and Message

These options apply for this modal:

Header and Sticky Header Height

Top Menu and Menu Item Font Size

 

Border Bottom Header, Sticky Header Height and color

Top Bar Background Color and Font Color (Header Widget Menu)

Extra Useful resources for Top Bar area