I had the same problem, Om Prakash Chowdhury helbed me on his blog by using some CSS:
https://allaboutbasic.com/2016/12/22/twenty-seventeen-theme-modifications-of-header-footer-sidebar-contents-and-documentations/
Instead of “red” you can use any colour, I chose #8655
div.site-branding.ats-align-left .wrap {
background: red !important;
}
The menu-question is not solved yet…
