Up until her Oscar-nominated role in Junebug in 2005, Amy Adams had blonde hair. The actress switched up her colour for the role, and has kept it ever since.
"Based on roles that I was getting called in for, people were responding to certain types of characters with me as a blonde," Adams told Allure. "The minute I went red, it was quirky and fun instead of flirtatious and dumb.
"It really changed things up. People began to see me in a different way, for different roles."
Mia Farrow's close-cut pixie, which became famous after her roles in Rosemary's Baby and The Great Gatsby, was a stroke of genius on her part.
"I had literally cut it myself earlier that year—with a pair of fingernail scissors—while working on the Peyton Place TV series at Fox Studios. This was long before I ever heard of Vidal Sassoon," said Farrow. "My then-boyfriend, Frank Sinatra, loved the cut, and so I kept it short."
Fresh out of BMX Bandits, Nicole Kidman burst onto the scene with her wild, curly red hair. The actress scored some fun roles, but things definitely changed when she straightened and smoothed out her hair in the early '90s. Her new slick red hair was made famous in roles like Practical Magic and Moulin Rouge!
Though Brigette Bardot had a fringe since the beginning of her career, her iconic blonde 'do with the sweeping fringe didn't come about until around 1956 when she was cast in Mio Figlio Nerone and was asked to dye her hair.
Kristen Stewart flirts between platinum white-blonde and brunette nowadays, but her natural colour is a mousy blonde. After doing some acting work as a teenager, Stewart dyed her hair a deep brown before being cast as Bella Swan in Twilight. She kept her brown hair for several years before switching things up by going short and blonde.
Although she scored a few minor guest appearances with her natural blonde hair, Emma Stone didn't make any waves until she went red. The actress originally dyed her hair to play her character in her breakout movie Superbad.
"Judd made me a redhead," Stone said in 2010. "I was a brunette during casting. Then Judd walked in, said 'Make it red,' and walked out. So he made me this way."
Like her spy character Black Widow, Scarlett Johansson is known for changing her hairstyle often. But the look perhaps most associated with her is her blonde waves, which earned her notoriety in roles like Vicky Cristina Barcelona, He's Just Not That Into You and Match Point.
Surprisingly, Johansson is naturally brunette. She made the switch to blonde in 2004.
In the very beginning of her career, Lucille Ball worked both as a blonde and as a brunette (her natural colour). Before landing the role of Lucy in I Love Lucy(which called for a redhead), Lucille dyed her hair—with henna!
"Lucy's hair was a golden apricot colour, and she used a henna rinse to achieve it," said Irma Kusley. "She met a very wealthy sheik who had heard about her problem getting the right colouring. He said he would send her a lifetime supply of henna, which he did! We kept it in my garage, locked away in a safe."
Rooney Mara made a very drastic hair-change when she took on the role of Lisbeth Salander in The Girl With The Dragon Tattoo. Cutting, dying and shaving her naturally long brunette hair, Mara's look was instantly more severe.
"I had parts of my head shaved," Rooney told Allure, "I was in that character for over a year. If you're going to do it, you have to do it. People always ask, 'Were you crying when they cut your hair?' And it didn't freak me out at all. I was really happy to do it."
After finishing the role, Mara kept her shorter, more 'serious' hair for several movies including Carol, The Secret Scripture and A Ghost Story.
In her first couple of roles (including The Social Network, 21 Jump Street and The Five-Year Engagement), Dakota Johnson sported a somewhat regular haircut, with long blonde layers and a middle part. In her preparation to play Anastasia Steele in Fifty Shades of Grey, Johnson went deep brown and cut bangs into her brunette hair, a look that she has kept ever since.
When Jane Birkin broke onto the scene in the 1960s, she made waves when she cut her iconic bangs, for which she is known for.
In 2010, Michelle Williams cut off her mid-length blonde curls in favour of a bleach-blonde pixie cut.
She explained to ELLE US at the time, that she had cut it for her late fiancé, Heath Ledger: "I cut it for the one straight man who has ever liked short hair and I wear it in memorial of somebody who really loved it."
In the eight years since, Williams has kept her hair short and blonde, including in roles like My Week With Marilyn, Manchester by the Sea and All The Money In The World.
Known for her iconic hair, Farrah Fawcett turned a corner in her career when she flicked out her blonde curls for Charlie's Angels. The style became known as the "Farrah hair" or "Farrah-flip".
Before Marilyn Monroe found fame as the world's most famous blonde bombshell, she was a natural brunette. Working as a model and actress in 1948, Monroe didn't find any major success until she dyed her hair a platinum blonde, and had her hairline raised by electrolysis. She went on to star in several iconic roles including Gentlemen Prefer Blondes and Some Like It Hot.
Famous for her red hair on Sex and the City, a lot of people were surprised to hear that Cynthia Nixon is not a natural redhead. Nixon kept the red for several roles, after it kick-started her career in 1998.
Before starting her role as Sansa Stark on Game of Thrones, Sophie Turner was a blonde. The young actress dyed her hair red before filming and has kept the colour since.
"As a redhead, I was originally really shy. I was 13 and changed my hair from blonde to red and I was like, 'Oh my God, this is so weird, this is not me'."
"But my role in Game of Thrones went from being a very vulnerable and insecure young girl to being a powerful woman who is very confident in herself and very empowered. So whenever I think of my red hair, I relate it to such a strong woman."
And of course, we'd be remiss if we didn't mention the famous transformation of Jennifer Aniston. Prior to her role on Friends, the actress sported long, brunette locks.
Created by her longtime friend and hairstylist Chris McMillan, not only did she influence millions of hairstyles but she also instantly rose to fame during and following the '90s sitcom.