I tryed the two products and both make a huge difference between yellow-ish hair and white hair. The only thing is I didn´t do a strand test before: I had freshly washed, dryed hair. Long story short, on some strands it was lilac and on some otherswhite. Better lilac than bleach yellow, but do a stran test before.
The instructions where however very clear and i have the best hair I could now. Use a good amount of conditioner on the following washes. The shampoo works also fine.