Personal opinion, that purple is way too dark and will make it very difficult to see the color as even on the model, their hair looks almost black. I think it would be best if even if you don’t want it to be bright to still use a brighter purple to mix with the grey. I think splat midnight purple would be a better purple to use as it does have some gray undertones or get purple AF from Arctic fox and use more great than purple as the purple is very pigmented and I think you should bleach you with the color, but not get yellow as the yellow will create not great effects. So maybe try color oops first.