// Set attribute name and value to search for
$attribute_name  = 'color';
$attribute_value = 'green';

$args = array(
	'post_type'      => 'product',
	'post_status'    => 'any',
	'posts_per_page' => -1,
	'orderby'        => 'title',
	'order'          => 'ASC',
	'tax_query'      => array(
		array(
			'taxonomy' => 'pa_' . $attribute_name,
			'field'    => 'name', // can be 'slug'
			'terms'    => $attribute_value,
		),
	),
);
$loop = new WP_Query( $args );
while ( $loop->have_posts() ) {
	$loop->the_post();
	// do stuff here... e.g. get_the_ID()
}
wp_reset_postdata();

// Set custom attribute name and value to search for
$attribute_name  = 'color';
$attribute_value = 'green';

$serialized_value = serialize( 'name' ) . serialize( $attribute_name ) . serialize( 'value' ) . serialize( $attribute_value ); // extended version: $serialized_value = serialize( $attribute_name ) . 'a:6:{' . serialize( 'name' ) . serialize( $attribute_name ) . serialize( 'value' ) . serialize( $attribute_value ) . serialize( 'position' );
$args = array(
	'post_type'      => 'product',
	'post_status'    => 'any',
	'posts_per_page' => -1,
	'orderby'        => 'title',
	'order'          => 'ASC',
	'meta_query' => array(
		array(
			'key'     => '_product_attributes',
			'value'   => $serialized_value,
			'compare' => 'LIKE',
		),
	),
);
$loop = new WP_Query( $args );
while ( $loop->have_posts() ) {
	$loop->the_post();
	// do stuff here... e.g. get_the_ID()
}
wp_reset_postdata();

add_action( 'woocommerce_email_after_order_table', 'add_payment_method_to_admin_new_order', 15, 2 );
 
function add_payment_method_to_admin_new_order( $order, $is_admin_email ) {
  if ( $is_admin_email ) {
    echo '<p><strong>Payment Method:</strong> ' . $order->payment_method_title . '</p>';
  }
}