Underneath hair color, also known as undertones, refers to the underlying color or shade of hair that is visible beneath the surface. It can be warm (e.g., gold, orange, red), cool (e.g., blue, purple, green), or neutral (a mix of both).
Understanding underneath hair color is crucial for color treatments, as it affects the final result. It can enhance or diminish the vibrancy of the desired color. Historically, hairdressers used bleach to remove natural undertones and create a clean canvas for coloring.