Fix dataTables data frame preview tab for dark themes

src/rstudio/_rstudio-dark.scss

@@ -303,12 +303,25 @@ table.rstheme_tabLayoutCenter, .rstudio-themes-flat .rstudio-themes-dark-grey .g
   }
 }
 
+/* hacky toolbars section */
 .rstudio-themes-flat .rstudio-themes-dark-grey {
   div.windowframe > div:last-child > div > div > div > div > div:not(.gwt-TabLayoutPanelTabs) {
-    /* hacky toolbars section */
     background: $ui-rstudio-tabs-inactive !important;
   }
 }
+/* Data Frame Preview */
+.dataTables_wrapper thead th {
+    background: darken($ui-rstudio-tabs-selected, 5%) !important;
+    color: $ui-rstudio-tabs-selected-color !important;
+}
+.dataTables_scrollBody table tbody td:first-child {
+    background: darken($ui-rstudio-tabs-selected, 5%) !important;
+    color: $ui-rstudio-tabs-selected-color !important;
+}
+.dataTables_info {
+    background: darken($ui-rstudio-tabs-selected, 5%) !important;
+    color: $ui-rstudio-tabs-selected-color !important;
+}
 
 /* scrollbars */
 .rstudio-themes-flat .rstudio-themes-dark-grey .gwt-TabLayoutPanelTabs,