Ok… I think I figured out my real problem. I will try to explain. I use the light color theme… but I change the header to black. The desktop header background is controlled by the “header background” color… but if I open it on a mobile phone… the header background is actually controlled by the “secondary” color.
EDIT: I think I figured it out. I created a component and added this to the mobile css…
.d-header {
background-color: var(--header_background) !important;
}