Index: wp-admin/custom-background.php
===================================================================
--- wp-admin/custom-background.php	(revision 22685)
+++ wp-admin/custom-background.php	(working copy)
@@ -330,6 +330,9 @@
 	$default_color = ' data-default-color="#' . esc_attr( get_theme_support( 'custom-background', 'default-color' ) ) . '"';
 ?>
 <input type="text" name="background-color" id="background-color" value="#<?php echo esc_attr( get_background_color() ); ?>"<?php echo $default_color ?> />
+<?php if ( current_theme_supports( 'custom-background', 'default-color' ) ) : ?>
+	<span class="description hide-if-js"><?php printf( __( 'Default: #%s' ), esc_attr( get_theme_support( 'custom-background', 'default-color' ) ) ); ?></span>
+<?php endif; // default-color ?>
 </fieldset></td>
 </tr>
 </tbody>