Sure, you can use this CSS from the Tracks CSS snippets collection:
body,
.excerpt,
.main,
.menu-primary ul,
#site-header {
background: #fff;
}
#menu-primary-items a,
#title-info a {
color: #000;
}
Please copy & paste the code above into the “Custom CSS” section in the Customizer (Appearance > Customize), and it should take affect right away.
That will make the background white and make the menu items and site title black. You can change the “#fff” color code to make the background a color besides white, and the “#000” value to change the color of the site title and menu items.