This code snippet uses the Map ID to customize the map styles in the User Locations extension.

um_user_locations_map_args_customize_05.php

<?php

/**
 * Use Map ID to customize the user location map.
 */
add_action( 'wp_footer', function () {
  ?><script type="text/javascript">

    function um_user_locations_customize_mapId( args, hash, directory ) {
      args.mapId = 'YOUR_MAP_ID';
      return args;
    }

    // customize the map in the member directory.
    wp.hooks.addFilter( 'um_user_locations_map_args_init', 'um_user_locations', um_user_locations_customize_mapId );

    // customize the map in profiles.
    wp.hooks.addFilter( 'um_user_locations_map_field_args_init', 'um_user_locations', um_user_locations_customize_mapId );
  </script><?php
}, 20 );

This gist is a part of the article User Locations - Hooks.
Related article - Use Map IDs.

You can add this code to the functions.php file in the active theme directory. Skip the opening <?php tag.