Anonymous wrote:A lot of it depends on the colors they're wearing and their makeup. If someone has typically been a blonde (Cameron Diaz, Margot Robbie, Emma Roberts from your examples), they don't know how to do their makeup to match the darker hair.
I'd also argue that some go far too dark; if they went a darker blonde/light brown, it would look more natural.
I think it's extremely funny that you think any of these women are doing their own makeup for these red carpet events where they were photographed, as opposed to having it done by a professional makeup artist who presumably does know how to do makeup to suit their hair. And in fact you can see that the makeup artists used the occasion of darker hair to do stronger brows, darker lips, etc. All of which would look totally overpowering on a blonde but work on a brunette. This is also a major reason actresses switch up their hair for events like this, because it shows directors range with their looks and can help them get roles that might initially seem counter to the looks they are best known for.