There are 3 processes that can be used to alter hair color, all of which can be done alone or used to support each other for a desired look. Before we talk about changing hair color let's first understand natural hair color.

 

Hair is made of 3 distinct layers; the outer layer, cuticle is nearly transparent like glass. Under the cuticle is the cortex which is a fibrous (like cotton) and opaque. The cortex is also where your natural hair color is, if your hair is red then the cortex is red, black the cortex is black, blond then blond cortex. The outer layer, cuticle, is always clear and you see the cortex (hair color) through it. Gray hair is a good example; hair turns gray because it no longer produces a cortex, only cuticle (clear) and medulla (white).