Reading constants in SCSS, modifying colors for Derpibooru variant

src/styles/colors.scss

@@ -1,4 +1,5 @@
 @use 'sass:color';
+@use 'environment';
 
 $background: #15121a;
 
@@ -55,3 +56,31 @@ $error-background: #7a2725;
 
 $warning-background: #7d4825;
 $warning-border: #95562c;
+
+@if environment.$current-site == 'derpibooru' {
+  $background: #141a24;
+
+  $text: #e0e0e0;
+  $text-gray: #90a1bb;
+
+  $link: #478acc;
+  $link-hover: #b099dd;
+
+  $header: #284371;
+  $header-toolbar: #1c3252;
+  $header-hover-background: #1d3153;
+  $header-mobile-link-hover: #546c99;
+
+  $footer: #1d242f;
+  $footer-text: $text-gray;
+
+  $block-header: #252d3c;
+  $block-border: #2d3649;
+  $block-background: #1d242f;
+  $block-background-alternate: #171d26;
+
+  $media-box-border: #3d4657;
+
+  $input-background: #282e39;
+  $input-border: #575e6b;
+}

src/styles/environment.scss

@@ -0,0 +1,20 @@
+@use 'sass:meta';
+@use 'sass:string';
+
+@function get-defined-constant($constant-name, $default-value: '') {
+  $resolved-value: $default-value;
+
+  @if meta.function-exists('vite-read-env-variable') {
+    $candidate-value: meta.call(meta.get-function('vite-read-env-variable'), $constant-name);
+
+    @if string.length($candidate-value) != 0 {
+      $resolved-value: $candidate-value
+    }
+  }
+
+  @return $resolved-value;
+}
+
+$current-site: get-defined-constant('__CURRENT_SITE__', 'furbooru');
+
+