crossword-8.x-1.x-dev/modules/crossword_colors/crossword_colors.module

<?php

/**
 * @file
 * Hooks for crossword_colors module.
 */

/**
 * Implements hook_library_info_alter().
 *
 * Adds the crossword-colors.css file to crossword.default library.
 * We just put this new stylesheet after the ones in the library instead
 * of trying make any replacements.
 */
function crossword_colors_library_info_alter(&$libraries, $extension) {
  if ($extension == 'crossword' && isset($libraries['crossword.default'])) {
    $uri = \Drupal::service('crossword_colors.service')->getCrosswordColorsCssUri();
    if ($uri) {
      $libraries['crossword.default']['css']['component'][$uri] = [];
    }
  }
}