btn-danger on switch will make it red for on and black for off

UI/Content/Overrides/bootstrap.toggle-switch.less

@@ -4,9 +4,17 @@
 .toggle {
   .slide-button {
     .buttonBackground(@btnDangerBackground, @btnDangerBackgroundHighlight);
+
+    &.btn-danger {
+      .buttonBackground(@btnInverseBackground, @btnInverseBackgroundHighlight);
+    }
   }
 
   input:first-of-type:checked ~ .slide-button {
     .buttonBackground(@btnPrimaryBackground, @btnPrimaryBackgroundHighlight);
+
+    &.btn-danger {
+      .buttonBackground(@btnDangerBackground, @btnDangerBackgroundHighlight);
+    }
   }
 }

UI/Series/Delete/DeleteSeriesTemplate.html

@@ -23,7 +23,7 @@
                                 <span>No</span>
                             </p>
 
-                            <div class="btn btn-primary slide-button"/>
+                            <div class="btn slide-button btn-danger"/>
                         </label>
 
                 <span class="help-inline-checkbox">