Red Hosts can replace regular Hosts in any area. Their skull is replaced by a vulnerable red material. Unlike normal Hosts, they can still take damage when lowered down, but will fire 5 blood shots instead of 3, and rise up more often.
Furthermore, unlike regular Hosts, Red Hosts are very vulnerable, even while they're lowered down before attacking. This will give the character a chance to defeat them as quickly as possible before their skull rises up to attack.