Here's a breakdown:
* What Permanent Hair Color Does: Permanent hair dye works by opening the hair cuticle (the outer layer), depositing dye deep inside the hair shaft, and then using a developer (usually hydrogen peroxide) to lift the natural pigment and allow the new color to take its place. The dye molecules are large and trapped inside the hair shaft.
* Why It's Not *Truly* Permanent: The color that has been dyed is there permanently, but it does not prevent new hair growth from coming in with your natural color. In the context of hair dye, *permanent* refers to the color will not wash out.
* The Issue of Roots: As your hair grows, your natural color will appear at the roots. This is the reason people need to touch up their "permanent" hair color every few weeks or months.
* Fading (Sometimes): While permanent color is designed to stay, some fading can occur over time. This is often due to factors like:
* Sun exposure: UV rays can break down the dye molecules.
* Washing: Frequent washing can gradually strip away some of the color.
* Harsh products: Shampoos with sulfates, for example, can contribute to fading.
* Damage: Damaged hair may not hold color as well.
In summary: You can't change the color your hair grows out of your head. However, you *can* permanently alter the color of the hair you currently have, but you'll need to maintain it with touch-ups to address root growth.