How to change the header color with App layout of angular components in AngularDart - dart

Question

How can I change the background color with app layout of angular components in an AngularDart project. I tried it but nothing affected the background blue color.
layout_component.html
<header class="material-header shadow">
<div class="material-header-row">
<material-button class="material-drawer-button" icon (trigger)="drawer.toggle()">
<material-icon icon="menu"></material-icon>
</material-button>
<span class="material-header-title">Mobile Layout</span>
<div class="material-spacer"></div>
<nav class="material-navigation">
<material-button class="material-drawer-button" icon (trigger)="">
<material-icon icon="favorite"></material-icon>
</material-button>
</nav>
<nav class="material-navigation">
<material-button class="material-drawer-button"
icon
popupSource
#source="popupSource"
(trigger)="basicPopupVisible = !basicPopupVisible">
<material-icon icon="more_vert"></material-icon>
</material-button>
<material-popup defaultPopupSizeProvider
enforceSpaceConstraints
[source]="source"
[(visible)]="basicPopupVisible">
<div class="basic">
Hello, I am a pop up!
</div>
</material-popup>
</nav>
<nav class="material-navigation">
<div href="#AppLayout">SIGN IN</div>
</nav>
</div>
layout_component.css
.material-header-row {
background-color: black;
}
.basic {
height: 200px;
padding: 16px;
}
Thank You

Answer 1

If you add the style to a parent component (AppComponent) you can use ::ng-deep to pierce through component style encapsulation boundaries (from parent into children)
::ng-deep header.material-header {
background-color: black;
}
Or to use your code example
::ng-deep .material-header-row {
background-color: black;
}
Update
For above selector, the specificity wasn't high enough to override the background color.
This worked for me:
::ng-deep header.material-header.material-header {
background-color: black;
}
If you add the styles to index.html, ::ng-deep isn't required.
Angular rewrites styles selectors added to components to match the classes like class="_ngcontent-qbq-3" it addes to each component (with a different number for each) to enforce style encapsulation.
Styles added to index.html are not rewritten and these classes are ignored.
You also might need ::ng-deep for HTML added with [innerHTML]="..." or someElement.append(...) because HTML added this way doesn't get the classes added and selectors for CSS added to components will therefore not match after the rewrite anymore.