GNOME #411427; Look for gtk-2.0/gtkrc in the theme directory and use it; found
in the Ubuntu package.

Index: gdm-2.18.1/gui/greeter/greeter_parser.c
===================================================================
--- gdm-2.18.1.orig/gui/greeter/greeter_parser.c	2007-04-09 07:15:10.000000000 +0200
+++ gdm-2.18.1/gui/greeter/greeter_parser.c	2007-05-02 18:09:17.000000000 +0200
@@ -1781,6 +1781,7 @@
   xmlChar *prop;
   gboolean res;
   GList *items;
+  char *dirtheme, *gtkrc;
   
   /* FIXME: EVIL! GLOBAL! */
   g_free (file_search_path);
@@ -1827,6 +1828,13 @@
       return NULL;
     }
 
+  dirtheme = g_path_get_dirname (file);
+  gtkrc = g_build_filename (dirtheme, "gtk-2.0", "gtkrc", NULL);
+  if (g_file_test (gtkrc, G_FILE_TEST_IS_REGULAR))
+    gtk_rc_parse (gtkrc);
+  g_free (dirtheme);
+  g_free (gtkrc);
+
   /*
    * The gtk-theme property specifies a theme specific gtk-theme to use
    */
