get_the_term_list( get_the_ID() label formatting?

You can use HTML to mark it up however you’d like. You can use a <strong> tag to make it bold:

$film_tags = get_the_term_list( get_the_ID(), 'film_tags', '<strong>Tags:</strong> ', ', ', '' );

Or add a class to style with CSS:

$film_tags = get_the_term_list( get_the_ID(), 'film_tags', '<span class="tags-label">Tags:</span> ', ', ', '' );