SFX Deep Purple mix

I mix different brands all the time, so no issues there.
Do you mean another colour for the undyed parts of your hair or something to put over the purple?
I know you don't want to bleach, but a mild bleach bath left on for just a couple of minutes will turn Deep Purple to a bright pink, which will give you more options with warm colours

A color to put over the purple, either a color I can mix with a tiny part of Deep Purple before applying or something that I can put straight on my hair once the colour has faded a bit more (right now it's still a rich purple). I was thinking about some blues, I guess they are the best colours for a mix like this?

I think blue is the obvious way to go if you don't want to force fade or bleach. A turquoise will make a lovely deep inky blue over a pink based purple.

Oh you just told me the thing I hoped! I was thinking about turquoise indeed but thought it would be too light to work with a purple and its fade. Definitely will give it a try!

It is what i would try. I think a darker blue would just go super dark over Deep Purple

Yeah I thought so too. I've only used dark blues like Directions Midnight Blue or Neon Blue on myself. I guess that a bit of Deep Purple combined with a blue would counteract the green fade, but since my base wouldn't be pale (and not a bleached blonde in any case) I'd probably end up with a very dark colour.