global: Made dark overlay darker.

marko/global/colors.less

@@ -19,7 +19,7 @@ body.theme-story {
     color: #4BF;
   }
   .color-highlight-dark {
-    background-color: rgba(0, 9, 18, 0.50);
+    background-color: rgba(0, 4, 9, 0.75);
   }
 }
 
@@ -40,7 +40,7 @@ body.theme-logs {
     color: #BBB;
   }
   .color-highlight-dark {
-    background-color: rgba(18, 9, 0, 0.50);
+    background-color: rgba(9, 4, 0, 0.75);
   }
   .color-highlight-primary {
     background-color: rgba(255, 187, 17, 0.25);
@@ -83,7 +83,7 @@ body.theme-data {
     color: #BBB;
   }
   .color-highlight-dark {
-    background-color: rgba(18, 8, 0, 0.50);
+    background-color: rgba(8, 4, 0, 0.75);
   }
   .color-highlight-primary {
     background-color: rgba(204, 204, 34, 0.25);