Here's why:
* Pigment: Black hair has the highest concentration of eumelanin, the pigment responsible for brown and black colors.
* Reflectance: Black hair absorbs almost all light wavelengths, which is why it appears black to the human eye.
* Color Spectrum: While dark brown hair can be very dark, it still reflects a bit more light than black hair, which allows us to perceive a difference in hue.
So, black hair is its own distinct color, separate from brown.