Final answer:
Hair coloring is a method of changing hair color for various cosmetic reasons, either through semi-permanent formulas that wash out over time or permanent methods that chemically alter the hair's structure. Semi-permanent coloring is great for subtle changes and blending grays, whereas permanent color provides a lasting change.
Step-by-step explanation:
Hair coloring or hair dyeing is the process of changing the natural color of hair. This change is typically done for cosmetic reasons, such as covering white or gray hair, following fashion trends, or retaining a natural hair color that has changed due to external factors. While some choose professional hairdressers for this service, there is also a significant market for at-home hair coloring products. Semi-permanent hair color is a popular choice because it allows for subtle changes and tones pre-lightened hair without creating a sharp contrast as the hair grows out.
Semi-permanent coloring washes out after a period, usually four to six weeks, allowing for less noticeable root regrowth. It is suitable for those who wish to avoid a stark difference between colored and natural hair, as it does not lighten the hair and provides a more natural look. Permanent hair coloring, on the other hand, involves a chemical process that changes the hair's structure and requires three components; a developer, a coupler, and an oxidant, resulting in a more lasting color.
The melanin pigment in hair determines its natural color and how it will respond to coloring. Permanent hair color can change this natural pigment, while semi-permanent hair color may not fully cover gray or white hair but can blend them to reduce their visibility.