However, we couldn't keep our eyes off the brunette Margot rocking a flawless US accent.
Whilst fans may be surprised to see Margot's darker hair, it's not the first time she's experimented as a brunette.
At the 2014 Oscars, the Wolf Of Wall Street star oozed old Hollywood glamour in a strapless black gown with her dark locks loosely curled.
Though she's known for being blonde, Margot revealed in 2014 that she'd had dark hair during her school years.
"I had it this colour all through high school actually. I always dyed it dark in high school. I was devastated when I had to go blonde," she mused to Elle in 2014.
However, when it comes to her enviable hair, Margot is always humble.
"I feel like my hair looks rubbish most of the time but thankfully if I ever have an event to go to there is always a hair stylist to sort it out!" she told marie claire UK in 2016.
"A trick I use if my colour is growing out is to spritz on Klorane Dry Shampoo, it's really good for adding texture and also helps disguise dark roots too."
And if you are a huge fan of the blonde, don't stress; photos from the set of her new Barbie movie have shown Margot has gone back to blonde since filming Amsterdam.
This article originally appeared on our sister site, Now To Love.