How to change Views field settings programmatically?

<?php

/**
 * Implements hook_init()
 * @see http://api.drupal.org/api/drupal/modules!system!system.api.php/function/hook_init/7
 */
function testModule_init() {

  // @see http://drupal.stackexchange.com/questions/49398/how-to-change-views-field-settings-programmatically

  $view_name = 'test_content_type_views';
  $view = views_get_view($view_name, TRUE);
  $view->display['page_1']->display_options['fields']['field_test_image_1']['settings']['colorbox_node_style'] = 'large';
  views_save_view($view);

  // later, commenting out the code above, and checking the values with dsm():
  $view_name = 'test_content_type_views';
  $view = views_get_view($view_name, TRUE);
  $image_field_settings = $view->display['page_1']->display_options['fields']['field_test_image_1']['settings'];
  dsm($view, '$view in '.__FUNCTION__.'()');
  dsm($image_field_settings, '$image_field_settings in '.__FUNCTION__.'()');

}