Icy colour advice please

[lisalockshair]

Hello! my next project is my friend below.. she currently has lagoon blue faded out on ends and bleach up top. she doesnt mind what she has as long as it is icey.. I was thinking about using the same lagoon blue but pastelising some of it to different levels and balayaging it through to give dimension.. the rest of the hair a really light pastel blue of the same pot.. but then the roots i am a bit stuck with.. she has regrowth and a slight orange tinge.. do i just bleach this up or would a shadow root look good? if so how do I do that?
thanks!
im in last year of training hence the non knowledge. Lucky I have lots of willing people to let me play! Would also love to know what anyone else would do.. these where just my inexperienced first thoughts!