diff -u b/core/modules/color/color.module b/core/modules/color/color.module
--- b/core/modules/color/color.module
+++ b/core/modules/color/color.module
@@ -95,7 +95,8 @@
 function color_library_alter(&$library, $name) {
   global $theme_key;
   $themes = list_themes();
-  $theme_libraries = $themes[$theme_key]->libraries;
+  $theme_libraries = $themes[$theme_key]->info['libraries'];
+  
   if (in_array($name, $theme_libraries)) {
     // Override stylesheets.
     $color_paths = \Drupal::config('color.theme.' . $theme_key)->get('stylesheets');