Try some new colors

src/app/components/shared/header/header.component.html

@@ -19,7 +19,7 @@
 
     <mat-menu #appMenu="matMenu" [overlapTrigger]="false">
       <button mat-menu-item (click)="logout()">
-        <mat-icon color="warn">exit_to_app</mat-icon>
+        <mat-icon class="warn">exit_to_app</mat-icon>
         <span>{{ 'header.logout' | translate }}</span>
       </button>
     </mat-menu>

src/app/components/shared/header/header.component.scss

@@ -3,3 +3,6 @@
   margin: 0 auto;
 }
 
+.warn {
+  color: #f44336;
+}

src/theme/_variables.scss

@@ -2,11 +2,11 @@
 // Define the palettes for your theme using the Material Design palettes available in palette.scss
 // (imported above). For each palette, you can optionally specify a default, lighter, and darker
 // hue. Available color palettes: https://www.google.com/design/spec/style/color.html
-$arsnova-primary: mat-palette($mat-indigo,500);
-$arsnova-accent: mat-palette($mat-amber, 500); //$mat-blue-gray, A200, A100, A400);
+$arsnova-primary: mat-palette($mat-teal,300);
+$arsnova-accent: mat-palette($mat-amber, 300); //$mat-blue-gray, A200, A100, A400);
 
 // The warn palette is optional (defaults to red).
-$arsnova-warn: mat-palette($mat-red);
+$arsnova-warn: mat-palette($mat-blue, 200);
 
 // Create the theme object (a Sass map containing all of the palettes).
 $arsnova-theme: mat-light-theme($arsnova-primary, $arsnova-accent, $arsnova-warn);