This was a traditional gumpaste that has egg white and gelatin in it, not the pastillage-type "gumpaste" that doesn't have gelatin. So again, I don't know if it will act the same way in anything other than this particular formula, but it's a guideline.
So to the business at hand...I had to use about a third of the jar to get the gumpaste the dark color that I ended up with. This was about as dark as it was going to get, so I stopped adding color to it and let it sit overnight.
This is it when I finished adding the color:
The next morning I checked, and lo and behold, it was still the same color as the aubergine. Huh. So it hadn't faded while wrapped up, and that was surprising, knowing how evil purple is.
Now it was time to do the flower, and since most colors fade when they dry, I was interested to see what would happen.
I made some petals and let them dry overnight. After twelve hours, this is what happened:
Yep, it faded. It didn't fade and turn blue, but it faded. It was noticeably lighter, just like the way I'd expect a dark gumpaste color to change. The issue with this is that I couldn't get the original gumpaste darker than it was by adding more color to it, so there isn't a way that you could start darker and have it lighten up and still be dark. It's going to be a light purple color when all is said and done.
So I ended up having to dust the petals anyway, and the search for a non-fading purple goes on...