Jeremy Herve on "[Plugin: Jetpack by WordPress.com] Display Carousel Images Full-Width on Mobile/iPhones?"

If you want to change the look of the carousel, you can dequeue Jetpack's Carousel scripts and styles, and load your own custom styles instead.

You can use the following functions to dequeue the Carousel scripts:

function changejp_dequeue_styles() {
    wp_dequeue_style( 'jetpack-carousel' );
    wp_dequeue_script( 'jetpack-carousel' );
}
add_action( 'post_gallery', 'changejp_dequeue_styles', 1001 );