Help ! Tone down highlights ?

[Catswhiskers]

Hi there, I've been having loads of fun highlighting at home with a friend ( we do eachothers) any ideas on how to tone down my 901s and 911 Majiblond with 813 majirel highlights (30 VOL), it's looking a bit warm on my natural dk blonde gold hair (level 6)and I was thinking about perhaps mixing a very ashy blonde 9,11 or 9,01 with a majiblond. I have a strong red undertone and always have to consider this when choosing colours otherwise they can look too warm and maybe brassy. I sometimes use Diacolor Blonde to reduce the warmth and bring it back to blonde.

Thanks for any help, I'm new to this site..