Allow Selectize input color css rules to be overloaded through iTop 3.0 themes

css/backoffice/vendors/_selectize.scss

@@ -3,6 +3,11 @@
  * @license     http://opensource.org/licenses/AGPL-3.0
  */
 
+$ibo-vendors-selectize-input--color: $ibo-color-grey-900 !default;
+
 .selectize-dropdown-content {
   max-height: unset; /* Overloaded as it will be handled by the _input-select.scss partial */
+}
+.selectize-input input{
+  color: $ibo-vendors-selectize-input--color;
 }