Hair color refers to the pigmentation of hair follicles, which is determined by the type and amount of melanin produced. The primary types of melanin are eumelanin, which can be black or brown, and pheomelanin, which is responsible for red and yellow hues. Common hair colors include black, brown, blonde, and red, with variations in shades and tones. Hair color can change naturally over time due to factors like aging, sun exposure, and hormonal changes. Additionally, people often choose to alter their hair color using hair dye or bleaching products, allowing for a wide range of creative expressions and styles.