This exploits a well-known fact about lighting -- someone illuminated by blue or violet light looks terrible, while someone illuminated by red light tend to loo

This exploits a well-known fact about lighting -- someone illuminated by blue or violet light looks terrible, while someone illuminated by red light tend to look better than they do under white light. This is why experienced photographers, shooting monochrome film and intending to flatter their subject, will use a red filter.