The 36-year-old Brit is much lauded for her impeccable style and her ever-changing hair styles. She's worn every length you can possibly imagine and then some, but rarely has the mama of one strayed from her natural cool-toned blonde.
That is - until now.
Sienna stepped out in New York this week debuting her brand new colour - a rich caramel so deep it appears almost brunette. The rich, creamy hue is perfect for the northern hemisphere which is heading into winter and surprisingly enough, looks equally as lovely as Sienna's regular blonde.
In fact, it is so very pretty that we've already called our fave salon to see when we can have ours done.
There's a couple of reasons why we want it so badly of course. Firstly, it's beautiful, natural and in a shade that suits pretty much all colourings. But secondly, it's the perfect way to give blonde tresses a break. You see, blonde takes work and it's hard on hair, often leading to damage such as splits and even breakage over the long term.
But a lovely sweet caramel such as this is not only more gentle on hair but requires less maintenance and is therefore less time-consuming and saves cash too.
Plus, it looks so amazing that even a life-long blonde such as Sienna would test it out. All in all, that's what we'd call a winner.