<?php
function cycle($a) {
    static $pointer = 0;

    $values = array_values($a);
    $pointer %= count($values);
    return $values[$pointer++];
}
?>
 

<?php
    $colors = array('fff', 'ccc');
    foreach ($some_data as $data) {
        echo '<span style="background-color: '.cycle($colors).'">'.$data.'</span><br />';
    }
?>