Add your own styles to Drupal's WYSIWYG module

ckeditor_styles.module

<?php
function ckeditor_styles_wysiwyg_editor_settings_alter(&$settings, &$context)
{
	if ($context['profile']->editor == 'ckeditor') {
		$settings['extraPlugins'] .= ',stylesheetparser';

		// Not necessary but removes all default styles from the CKEditor.
		$settings['stylesSet'] = array();
	}
}