diff --git a/core/modules/block/css/block.admin.css b/core/modules/block/css/block.admin.css
index 25c32b2ae862279d7e1daecf47ad42790f90de72..fe5ab05b78f523b90cf63248091efceb54268bcc 100644
--- a/core/modules/block/css/block.admin.css
+++ b/core/modules/block/css/block.admin.css
@@ -13,6 +13,7 @@
   margin-top: 4px;
   margin-bottom: 4px;
   padding: 3px;
+  color: #000;
   background-color: #ff6;
 }
 a.block-demo-backlink,
diff --git a/core/themes/stable9/css/block/block.admin.css b/core/themes/stable9/css/block/block.admin.css
index 25c32b2ae862279d7e1daecf47ad42790f90de72..fe5ab05b78f523b90cf63248091efceb54268bcc 100644
--- a/core/themes/stable9/css/block/block.admin.css
+++ b/core/themes/stable9/css/block/block.admin.css
@@ -13,6 +13,7 @@
   margin-top: 4px;
   margin-bottom: 4px;
   padding: 3px;
+  color: #000;
   background-color: #ff6;
 }
 a.block-demo-backlink,