What legal reason(s) do you have for needing to see their appearance when making a decision on whether to hire them? You may have some, such as requiring a professional appearance. These need to be spelled out in the job requirements. It also opens the doors to claims of illegal discrimination, since this will be on full display. In the US, that includes race, age, and gender. Having a required video can also reveal protected classes like familial status and religion, depending on what's in the background.

Whether an action is "Legal" is almost always dependent on context, and the lawyers/courts involved. A common tactic by racist nightclubs is to set a dress code, particularly on shoes. The argument is they aren't refusing entry based on race, but on clothing. But the unauthorized shoes are the ones commonly worn by people of the race they're discriminating against. Different courts have made different rulings on whether this (and similar actions) constitute racial discrimination.