Any idea what colour this is?

If i were trying to replicate it i would try adore Aquamarine. These types of turquoise are very dependant on base colour though.

Oh my local hair shop sell Adore so I'll pick some up. Do you think adding a touch of Enchanted Forrest by Manic Panic will give it a more of a greeny colour? My base is quite pale blonde on one side & more yellow/orange blonde on the other. I'm planning on doing a BB in about 3 weeks to even up the colour.

Looks like either an aquamarine or a faded blue over a yellowy base.  Very nice effect  🙂

I get this kind of colour mixing green and blue, but I've tried many different brands over time, couldn't tell which would give *exactly* this, and in what proportions - since I do my mixes by the eye and it always comes out a different hue.
At the moment I'm quite close to this with joico k-pak dye, a bit more than half of green, a bit less than half of blue. On a base of mostly natural white hair.

I've just done my hair directions alpine green and its come out a lot like this.

I've done Manic Panic Enchanted Forest and it came out almost identical but I was starting with a slightly more yellow blonde.