How to achieve a blue with purple fade using Directions

Hello everyone! I have been searching for something to replace my beloved SFX Blue Velvet while the worldwide shortage (discontinuation? I've heard mixed rumours in my city from retailers...) is happening. My biggest problem is that I have long hair, so my ends have YEARS of BV built up on it, and every dye I've tried on my roots has been too light/fading like mad compared to SFX. I just remembered that Punky Colours (I think it's called Directions in the UK?) has pretty good longevity, but I remember the Midnight Blue fading green on me when I used it years ago, which is not the look I'm going for.

So my main question: If I mix in a bit of one of Direction's purple dyes in with Midnight Blue, will that be a good way to achieve a purple fade instead of a green one? Or is the green fade inevitable?

Thank you in advance for any ideas! I'm getting married next year and would love to get this sorted out before the wedding. As it stands I have a lovely colour on my ends and a pale, quickly fading baby blue on my roots from the not great quality dyes I've tried...not a great look  😮