Ive got a Suburu impreza wagon wrx (auto) 1995

I have a standard coil flamer kit but have seen other scoobs with a rich blue flame instead of my orange one.
I spoke to someone about it and they said that what they do is have a relay switch attached to the negative feed of the coil packs from the ecu.
Is this possible?
If so does anyone know which wire it is?

Thnaks for any advice