Currently, there are not (as far as I have encountered) any uses for essence brews on violet and red potions. You create your stock and then throw the dust in and move on (RP and IG alchemical theory aside).
I'd like to propose an alteration to the model that would give alchemists a bit more creative flexibility and hopefully add some potential tactical/logistical interest when it comes to creating potion effects. I think that different herbs added to the essence brew could delay the onset of the individual effects by some amount of time; with different herbs affecting different potential effects and the strength of the delay.
Effects for essence brews of Amethyst and Ruby potions
Moderator: Developers
Re: Effects for essence brews of Amethyst and Ruby potions
Dragon breath is an amethyst(violet) potion that makes use of essence brews.