My hair is dark blonde (level 8) and the fringe is light blonde (level 11). It did the job on the dark blonde, as blue shampoos are mainly for darker shades, but nothing special on my platinum strands. I had some red, warm tones which it removed, leaving a nice, natural sandy tone in my hair, except for the root area where some warm undertones were still visible even after use.
It is definitely a good product, it mostly delivers on its promises. For hair types like mine (dark), it is definitely more effective than purple shampoos. I suspect that in order to achieve completely natural, intense cool tones, this blue shampoo should be used with the anti-brass toner from the same brand or another toner that neutralizes red tones.
I would buy it again.

I think it is the best shampoo for its price to remove yellow tones and if someone wants cooler colors. It stings a little in the eyes if you leave it on for a long time and it runs, but it washes away with a little water. It takes 5 minutes to take effect, so it's good to have some music in the bathroom...

Very good for what it promises, better result even than the purple ("So Silver") of the same series, on 85% white hair + with highlights (yellowish) on the ends. Unfortunately, it caused an allergy on my lower eyelids, even though I am not generally allergic. I recommend a sensitivity test before use, but otherwise very good.