<?php
    echo '<span class="entry-utility-prep entry-utility-prep-cat-links">Рубрика:</span>';
    $cats = array();
    foreach((get_the_category()) as $category)
    {
        $class_link='normal';
        if($category->name=='Вторая')
        {
            $class_link='selected';
        }
            $category_id = get_cat_ID( $category->cat_name );
            $category_link = get_category_link( $category_id );
            $cats[] = '<a href="' . $category_link . '" class="' . $class_link . '">' . $category->cat_name . '</a>';
     }
     echo implode (', ', $cats);
?>

<?php printf( __( '<span class="%1$s">Рубрика:</span> %2$s'), 'entry-utility-prep entry-utility-prep-cat-links', get_the_category_list( ', ' ) ); ?>

  <?php
    echo '<span class="entry-utility-prep entry-utility-prep-cat-links">Рубрика:</span>';
    foreach((get_the_category()) as $category)
    {
        $class_link='normal';
        if($category->name=='Вторая')
        {
            $class_link='selected';
        }
            $category_id = get_cat_ID( $category->cat_name );
            $category_link = get_category_link( $category_id );
            echo '<a href="' . $category_link . '" class="' . $class_link . '">' . $category->cat_name . '</a>';
        }
?>