Hello,
To change background color of the header you need to add this code in custom.css file.
.header-wrapper{
background: red;
}
Could you please clarify with more details which styles of header size and logo position you want and show us screenshots?
Here is a video tutorial how to create custom.css: https://www.youtube.com/watch?v=Qok2zRedRMY&feature=youtu.be.
Regards,
Robert Hall.















