"Changing my hair for roles is liberating, even if it's not always a look I would go for. Dying you hair is like getting tattoos. Once you start you won't stop," contactmusic.com quoted Watts as saying.
"I started in my twenties, but all the travelling I do makes it tricky, as I don't always see the same persona and blonde is a difficult colour to get right," she added.
"The Impossible" actress also likes to experiment with make-up and even though her beauty routine is limited, she is a big fan of making a statement with a slick of dramatic red lipstick.
"I am hopeless at applying make-up. Luckily, I don't wear much anyway and, for ease, I get my lashes and brows tinted. I only have a concealer, cream blush and lipstick in my purse. A make-up artist friend gave me some Burberry beauty products, which are fantastic.
"I am really enjoying red lips again, but they can look quite harsh in photographs," said the 44-year-old.