Doutzen Kroes is undoubtedly one of the most beautiful
people elves on the planet. She usually has light blond hair but there was a time that she had darker hair, which was dark blond or even brown. In dark blond she looked more natural and wasn't so angelic.
According to L'oreal, to get that look you should use this colour:
I post one picture of Doutzen in light blond for you to compare:
I do admit that she looks gorgeous no matter what colour she has on her head.