I've not used it but I've heard of it being done. You can find info on Google.
Seems you need very little, 10 drops or so for a 1 lb batch.
Might turn a bit blue or even stain skin, I would probably start with way less just to be on the safe side.
Always wanted to try it but purple isn't a color I use often. Should just do it since I have the gentian violet sitting around.