When selecting purple hair dye, consider how long you want the color to last. Hair color dye is intended to wash out after one day, making it ideal for testing, and application is as simple as a spray or pomade. Semi-permanent dyes, in contrast hand, use a conventional registration process and will fade after a few weeks, but perpetual dyes will last until your hair grows out. Alternatively, you can dye it again.
It is also crucial to remember that the concentration of the purple color will be greatly affected by your current hair color. Those with light hair will get the most vibrant results, while those with brown hair will get a more nuanced purple sheen, which will be most visible in sunlight. If you want darker results (and you're not a light blonde), you should bleach your hair before applying purple dye. However, because this can be a complex process, you should carefully research how to safely decolorize your hair yourself before deciding to go ahead with it. It will be fantastic if you experiment with the best purple hair dye for dark brown hair.