Alternating post background colour

Is there a way to alternate the background colour of posts on the home page ?

Here’s my current loop:

<?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post(); ?>

        <div class="post1">

            <div class="left">
             <?php echo get_the_post_thumbnail($page->ID, array(170,170)); ?>
            </div>

            <div class="right">

            <h2><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>

            <small><?php the_time('jS')?> of <?php the_time('F')?>, <?php the_time('Y') ?></small><br /><br />

            <p><?php the_content(); ?></p>

            </div>

        </div>

<?php endwhile; ?>

<?php next_posts_link('&laquo; Older Entries') ?>
<?php previous_posts_link('Newer Entries &raquo;') ?>

<?php endif; ?>

All help is appreciated !