What type of hair color is considered semi-permanent?

Semi-permanent hair color is characterized by its ability to deposit color into the hair without the use of ammonia and typically does not contain a developer, which means it doesn't have a lasting effect like permanent dyes. Direct dyes are a subset of semi-permanent colors because they are applied directly to the hair and can penetrate the hair shaft slightly, resulting in color that lasts several weeks without needing a chemical reaction with a developer.

In contrast, permanent dyes contain ammonia and require a developer, leading to a more lasting color change that can endure until the hair grows out. Temporary dyes are designed for short-term use, often washing out after a single shampoo, while lightening agents are not color deposits at all but rather chemicals designed to lift the natural pigment from the hair.

Thus, choosing direct dye captures the essence of semi-permanent hair color, as it applies rich, vibrant colors without the long-lasting implications of permanent dyes.