You don’t always need to bleach your hair to have white hair (especially if you already have natural blond hair of course).
Semi-permanent toners are ineffective versus purple (or blue against orange) shampoo for yellow reflects.
I have white hair (like snow, not platinium or silver) and I do this on my own with 12/81 with 30 vol peroxide. I use purple shampoo when I have yellow reflects but with moderation for not have pink reflects.
Revlon’s spray against yellow reflects can help you too.
Be careful : oil, eggs and all yellow products you can put in your hair must apply yellow reflects.
Cigarettes’s smoke can do that too.
Good luck for White hair :)
PS : Please excuse my bad english, I’m french…