What is the difference between semi-permanent and permanent hair color?

The correct choice highlights a fundamental distinction between semi-permanent and permanent hair color in terms of how they interact with hair. Semi-permanent color is designed to deposit color onto the hair without altering its structure significantly. It generally lasts for several weeks and gradually fades with washing, as it doesn't penetrate deeply into the hair shaft. This fading is a key feature of semi-permanent color, making it less of a commitment for individuals who prefer to change their hair color frequently.

On the other hand, permanent hair color involves a chemical process that opens the hair cuticle to allow color molecules to penetrate the hair shaft, altering the hair’s structure. This type of color does not wash out and will require regrowth or maintenance with touch-ups at the roots as the natural hair color grows back.

The other options do not accurately reflect the properties of each type of hair color. Option A misrepresents the longevity of the colors; option C incorrectly suggests that permanently colored hair cannot be changed, when in actuality, it can be re-colored or removed through various methods; and option D presents a false comparison regarding maintenance requirements, as semi-permanent color tends to require less upkeep compared to permanent color, which needs regular touch-ups.