You should be able to:
editor.execute( 'highlight', { class: 'marker' } );
editor.execute( 'highlight', { class: 'marker-green' } );
editor.execute( 'highlight', { class: 'marker-pink' } );
editor.execute( 'highlight', { class: 'pen-red' } );
editor.execute( 'highlight', { class: 'pen-green' } );