gray.module

<?php

/**
 * @file
 * Make the site into black-white-gray style.
 */

/**
 * Implements hook_menu().
 */
function gray_menu() {
  $items = array();
  $items['admin/config/gray'] = array(
    'title' => 'User Black-White-Gray Style',
    'description' => 'Make the site into black-white-gray style for some unfortunately reasons, wish no one will use this module',
    'position' => 'right',
    'weight' => -5,
    'page callback' => 'drupal_get_form',
    'page arguments' => array('gray_style_enable_settings'),
    'access arguments' => array('administer site configuration'),
    'file' => 'gray.admin.inc',
  );
  return $items;
}
/**
 * Implements hook_preprocess_HOOK().
 */
function gray_preprocess_html(&$variables) {
  // Add css class 'gray' to the html tag.
  $enabled = variable_get('gray_style_enable', FALSE);
  if ($enabled) {
    $variables['classes_array'][] = 'gray';
  }
}