While we weren't looking Olivia Palermo stole Blake Lively's hair

Olivia Palermo has gone blonde. This is not a drill. This is real life.

Previously, Palermo was known for her rich, perfectly tonal brunette hair colouring – the kind that looks like it was painted strand-by-strand by a very well paid artist. But she has secretly been lightening her hair over the course of several months. We didn’t notice at her wedding, because we were too distracted by her bridal jumper. We didn’t notice at Couture yesterday because she had it pulled back. But then today she stepped out at the Elie Saab Haute Couture show looking like this:

Olivia Palermo at Elie Saab. Via Getty

We know what you're thinking. You're thinking, 'Maybe she just looks blonder because she's wearing her hair all wavy and tousled'. But now I present you with exhibit B:

Olivia Palermo at Valentino. Via Getty

This was taken on the same day at the Valentino Couture presentation - yes, OP gets her hair blow dried twice a day. That's just the kind of OG she is.

This has been a whopping Couture Week for hair revelations. First there was Kristen Stewart. Then there was Catherine Martin. Then there was Elsa Pataky. It's great, but we're getting a bit exhausted.

Click through this gallery to see what beauty and fashion looks Olivia's fellow famous Couture Week guests have been rocking:

What do you think of Olivia's new hue?