FIJISettingsViewer: fix setting of background colors of net entries

bin/Tk/FIJISettingsViewer.pm

@@ -1029,6 +1029,7 @@ sub _add_fiu ($$) {
         -balloonposition => 'mouse',
         -msg             => FIUMAP->{'FIU_DRIVER_PATH'}->{'help'} . " [" . FIUMAP->{'FIU_DRIVER_PATH'}->{'ini_name'} . "]",
     );
+    $widget_ro_background = $drv_entry->cget('-readonlybackground') if !defined($widget_ro_background);
 
     # Menu to select the fault model implemented by this FIU
     my $model_menu = $fr_fiu->Optionmenu(
@@ -1879,7 +1880,7 @@ sub _indicate_warning ($$) {
         # Work around: store the entry background color at creation time and
         # use that instead.
         my $bg_color = ($widget->cget("-state") ne "readonly") ? $widget_background : $widget_ro_background;
-        $widget->configure($bg_option => $widget_background);
+        $widget->configure($bg_option => $bg_color);
         delete $self->{'highlit_widgets'}->{$displaygroup}->{$name} if defined $self->{'highlit_widgets'}->{$displaygroup}->{$name};
     }