As I am aware, alkanet only makes a greyish purple. Search for ombre soap on youtube and watch the video by la fille de la mare...
The instructions for the root powder on brambleberry is 1 tbsp per 4 oz of oil and then to use 2 tbsp for 3 lbs of soap. This is what I have done. I made my infusion, let is set a week but then learned I can either wait 4-6 weeks for the infusion or use warm heat water bath like a crock pot on low for 30-60 minutes , so I did that too. I did strain my alkanet with some cheese cloth, b/c there was about a quarter inch of sediment in my infusion. I can't remember how much infusion I made, probably 16 fl oz. I read an easier way is to get a knee high stocking and use that. This way you can pour a lot more at a time and then squeeze more oil out of it. It took forever to strain it in cheese cloth and I had to change it several times - probably 30 mins to an hour...
I used my infusion for the first time making a layered soap. my darkest layer turned out to be an oily mush after about 16 hours, while my white layer was hard. I think I may have overdone it with the infusion. I didn't follow the 2tbsp/3lbs of soap as the person I was using as inspiration didn't either. I think I used waaaaayyyyy too much of the infusion in the darkest layer.