debug notices – wp_register_script was called incorrectly

Please update your plugin like this:

function reg_scripts() {
    $script_path = $this->plugin_url . '/javascripts/jquery.colorbox-min.js';
    wp_register_script( 'colorbox', $script_path, array('jquery') );
}
function add_filters_and_hooks() {
    add_action('wp_enqueue_scripts', array( $this, 'reg_scripts' ));

https://wordpress.org/plugins/smart-youtube/