Dip dyeing

I'm afraid you won't get a pastel pink or turquoise over that, it's too orange. For those colours you'd need to lighten it further and then tone to white. Was that part previously dyed?

My whole hair was dyed a very dark brown and had been for years with lots of build up, I agree that picture does make it look more orange than it actually is. To be honest I'm not willing to lighten my hair any further, not for a long time anyway, and I'd rather not dip dye it a bright colour.
Thank you for the help though, maybe in a few months ay 😛

You could get a light pink over that base as long as you don't mind it being more peachy/salmon toned (just call it Rose Gold lol and you are bang on trend) A very cool toned pink diluted (Rose Red, Virgin Rose etc) will give the best results on an orangey base.
If you put a light blue on it will pull much greener. Don't  use a turquoise it will just go straight up green.
Toning with diluted violet dye will help to get a better base for either of those colours
To avoid a harsh line you just need to blend it well. if you put conditioner on the area you don't want to dye, you can blend the dye up into it. also as you want a light colour you could dilute it more than you want and build the colour up in layers, then you won't have to worry about harsh lines.

Okay, a salmony colour could work, I quite like the idea of that actually, thank you very much 🙂

You could try a colour remover. It might remove some more of the orange tones.