I want to dye my hair a dark purple?

If you go to a salon or are able to purchase professional hair color, go for a level 4RV or 3RV. Your hair should darken to an eggplant shade. To intensify the purple color, I've found Manic Panic produces the most accurate, longest lasting results when you apply heat to the color when it's on your hair and rinse with cold water. If you don't want it to be a brighter, more intense purple, lighten your hair to blonde and use the Manic Panic. However, be prepared for it to fade much faster if you go that route.