Hi there,
for Tags you would use this:
add_filter( 'body_class', 'add_tags_to_body_class' );
function add_tags_to_body_class( $classes ) {
if( is_single() && $tags = get_the_tags( get_queried_object_id() ) ) {
foreach( $tags as $tag ) {
$classes[] = 'tag-' . $tag->name;
}
}
return $classes;
}
Archive pages automatically add the tog-term
class to the body.
But the blog itself does not – so i am not sure what you require there.