Hello :-)
Well, I think your asking is about to remain dead letter !
I do love violets, I will never be crazy enought to cut hundred of them just to dye a dress: NO WAY ! Sorry for that. Anyway, I don't have hundred of them :-)
What about growing yourself violets for that ?

All the best :-)

PS: asking all posts and making some I feel as beeing a kind of throll :-/ Where are all violet's fan ????

Have you done a test drive on usuing violets for dye?

Some plants don't come true to petal color. I am not a very experienced natural dyer, but I have done a few. Concord grape gives a nice purple. I have 100's of violets here, but they are pale purple.

I am curious to see how this turns out. Could you update me on your progress?Thanks,
Robin

And how fast would the colour be, I wonder?

Interesting question, though; not one I've heard before.