Flexform FAL image with image palette

FlexForm.xml

<settings.advertising>
      <TCEforms>
          <label>LLL:EXT:dw_page_types/Resources/Private/Language/locallang_db.xlf:flexform.plugin.event.advertising</label>
          <config>
              <type>inline</type>
              <maxitems>1</maxitems>
              <minitems>0</minitems>
              <foreign_table>sys_file_reference</foreign_table>
              <foreign_field>uid_foreign</foreign_field>
              <foreign_table_field>tablenames</foreign_table_field>
              <foreign_label>uid_local</foreign_label>
              <foreign_sortby>sorting_foreign</foreign_sortby>
              <foreign_selector>uid_local</foreign_selector>
              <foreign_selector_fieldTcaOverride type="array">
                  <config>
                      <appearance>
                          <elementBrowserType>file</elementBrowserType>
                          <elementBrowserAllowed>jpg,jpeg,png</elementBrowserAllowed>
                      </appearance>
                  </config>
              </foreign_selector_fieldTcaOverride>
              <foreign_types type="array">
                  <numIndex index="2">
                      <showitem>--palette--;LLL:EXT:lang/locallang_tca.xlf:sys_file_reference.imageoverlayPalette;imageoverlayPalette,--palette--;;filePalette</showitem>
                  </numIndex>
              </foreign_types>
              <foreign_match_fields type="array">
                  <fieldname>eventAdvertising</fieldname>
              </foreign_match_fields>
              <appearance type="array">
                  <collapseAll>1</collapseAll>
                  <newRecordLinkAddTitle>1</newRecordLinkAddTitle>
                  <headerThumbnail>
                      <field>uid_local</field>
                      <height>64</height>
                      <width>64</width>
                  </headerThumbnail>
              </appearance>
          </config>
      </TCEforms>
  </settings.advertising>