My sister is black, and wanted blue streaks!!
It took some lifting, came out patchy!! Some areas went pale green when lifting presumed cause she had blue black on previous!!
The pale green didn't bother me though has I already said that I would probably not be able to achieve it this time, I used /28 in wella as this was a green/blue.
I know next time I would get blue, cause I've done it before, I just use directions colour pots!
You could lift to a orange apply red, and a week later if still red apply blue and it should come out purple as red and blue is purple. Then all future colours can be purple. Ive done this on sister and it worked for me!!