Make site icon respond to theme

website/_includes/nav.html

@@ -1,7 +1,10 @@
     <header class="navbar bg-body-tertiary">
       <nav class="container">
         <a href="/" class="navbar-brand fs-4">
-          <img class="mt-n3" height="36" src="/assets/img/logo.svg" alt="Site icon">
+          <svg class="mt-n3" height="36" width="132.35" xmlns="http://www.w3.org/2000/svg">
+            <title>Site icon</title>
+            <use href="/assets/img/logo.svg#Ebene_1" fill="blue" />
+          </svg>
         </a>
         <div class="d-flex mb-3 mb-md-0 me-md-auto">
           <div class="btn-group">

website/_sass/base.scss

@@ -27,6 +27,14 @@ $table-bg: $palette4;
 $body-secondary-bg: $palette2;
 $body-tertiary-bg: $palette1;
 
+.cls-1 {
+  fill: $palette3;
+}
+
+.cls-2 {
+  fill: $palette2;
+}
+
 // If you want to provide the Ubuntu font, place those font files in assets/css/font
 
 /* ubuntu-mono-regular - latin */