I used Goldwell Oxycur Platin bleach with Goldwell Topchic Developer 9% 30 vol. I backcombed each section of hair before applying the bleach, wrapped it in foil and then left it to develop for about 40 minutes, rinsed it out, washed and conditioned and then dried it. This was how it looked after this step.
1 cup of white conditioner (it's important that it's white)
2 teaspoons of Manic Panic Ultraviolet semi permanent hair dye (or any other purple hair dye)
Mix it all together until you get a very scary bright purple shade and coat your hair. I used a colouring brush and also massaged it in with my hands. I left it for about 10 minutes (at which point I started to freak out that my hair had turned purple) and then washed it out and conditioned, dried and styled and this was the result.