I need to do augergine roses for a wedding cake. I will be making fondant/gumpaste roses
and would like to know where I can get this color gel, powder, or whatever to achieve
this dark color. I'm sure someone must have needed this at sometime. I recently did a wedding cake
but couldn't achieve the right tint. Is there a gel this color or do I need to mix it and shade
with dust? Any help will be greatly appreciated.

make/buy red fondant....make navy fondant...knead the red into the navy a little at a time until you get the shade you want.

Sugarflair Spectral Concentrated Paste Colour has a colour called grape violet. I use this colour a lot to achieve a dark eggplant colour. You can also add red if you're looking for more of a redish purple. I'm not sure where you are located, but if you Google it, it will show up.

Alternatively, I either tint the gumpaste a light purple and dust dark purple petal dust once dry. Or ... if you have an airbrushing kit, you can add black to purple to get a deeper colour.

Good luck

You can achieve it by mixing both navy/blue and red fondant/icing. and then add red or blue depending on the shade you like(light or dark)

Crystal Colors & GSA makes Aubergine petal dust. That's where I got mine.