Purple peanut butter

Hello! First time poster here. I want to make a vegan cheesecake for a friend that LOVES Gengar and like the flavour of crunchy peanut butter I was thinking about making the top of the cheesecake with the peanut butter, I wanted to colour it purple and draw with chocolate Gengar's eyes and smile. I'm afraid that a normal food dye wouldn't behave like I want with the colour of the peanut butter, does anyone have a suggestion? Thanks! submitted by /u/PopiPopi0808