I am asking on behalf of a friend about what colour this is or how to achieve it. Thanks in advance. 

Cake found on Pinterest 

I made a very similarly coloured buttercream recently - I used a tiny amount of Americolor's Ash. 

Thank you. 

No problem! Good luck with getting your colour matched   :)

Maybe the teensiest little bit of light blue added would bring out the blue tones in the ash a smidgeon more. Looking forward to seeing your finished product! 

Wilton makes a Delphineum blue that is that exact color.  It is beautiful and only takes a very tiny amount to achieve that color.

Was going to say the same thing. It comes in the Garden color set. Not easily found any more, but I got mine at Joann's fabrics. Love the whole set!

Thank you for your help. My friends son has asked her to make the cake but not for a while so she has time to practise. I will help her if needed. I have been searching online and that colour in americolor only seems to be in a set. We're from the UK so won't be as easy to source on its own. Will look the Wilton delphinium. Thanks once again for your help.