Loop with 2 categories

The template tag, query_posts(), detail the various arguments. Show all posts in category 2 AND 6:

<?php
$args=array(
  'category__and' => array(2,6)
  'post_type' => 'post',
  'post_status' => 'publish',
  'posts_per_page' => -1,
  'caller_get_posts'=> 1
);
$my_query = null;
$my_query = new WP_Query($args);
if( $my_query->have_posts() ) {
  echo 'List of Posts';
  while ($my_query->have_posts()) : $my_query->the_post(); ?>
    <p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></p>
    <?php
  endwhile;
}
wp_reset_query();  // Restore global post data stomped by the_post().
?>

Thanks for the answer, but it’s not the code i want.
I’d like to show only the 6 posts in the cat id 2 and 6, and to be equal posts: 3in id:2 and 3in id:6.
in the code below it show the 6 (img) posts randomly, but not equals with cats id 2&6!!! how can i do it, with only one loop.

<ul>
	<?php query_posts('cat=2,6&orderby=rand&showposts=6'); ?>
	<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>

		<?php //call the custom field "image1" //
		$var_img01 = get_post_meta($post->ID, "image1", TRUE);?>

	<li>
		<?php // Insert the custom field "image1" //
			if ( $var_img01 ) { ?>
				<a href="<?php the_permalink() ?>">
					<img src="<?php echo $var_img01; ?>"/>
				</a>
		<?php } else { ?>
				<img src="<?php bloginfo('stylesheet_directory'); ?>/images/no-image.jpg"/>
		<?php } ?>
	</li>

	<?php endwhile; else: ?>
		Oops, there is no pruduct in this page!!!
	<?php endif; ?>
</ul>

Thanks

Please review the examples here:
https://codex.www.ads-software.com/Template_Tags/query_posts#Category_Parameters