You will have to roughen up the surface first to get mechanical adhesion.
Even if you're color weary, your stylist can recommend a few looks that will help roughen up the hair cuticle.
Even if it doesn't seem necessary, sanding will roughen up the area, allowing the paint to better adhere to the surface.
The rocks project in innumerable bosses and crags, which roughen the sides and crests of the ridges.