Oh FFS blonde dye has made my hair look like I've had a blue rinse. What can I do now and in future?

[ScreamingBeans]

My hair is very nearly white, but I usually put a light blonde shade in it to take out that very harsh whiteness. I only do this about every 3 or 4 months because the roots blend in so well.

Today I did what I normally do and obviously left it on too long because now the top bit of my head looks like Phyllis from Coronation Street while the lower bits are blond.

What can I do? And is there anything that I can put on my hair in future, that will make it look blond without the risk of it going blue?

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I used to use Fanola Shampoo when I was blonde I'm not sure if that would help you.

I left the dye on too long one night before an important meeting and it went blue. I used head and shoulders to tone it right down.