Also described as: espresso hair, deep brunette
A deep, rich brown that can look almost black in low light.
typical range
An illustrative approximation, not a fixed definition.
Commonly leans warm, though genuinely cool-toned dark brown also occurs.
Fine warm or red undertones are often only visible in direct sunlight.
Hair colour, including grey and white hair, is not a reliable indicator of age and is never presented here as something to correct — it's one more colour to plan around, the same as any other.
Styling ideas below are optional and editorial — never rules, and never a claim that one colour choice is objectively correct for anyone.
Dark brown hair has a lot of eumelanin, but slightly less or a larger share of the brown form than black hair, so a little light does make it through a strand and back. That transmitted light is filtered by the pigment and emerges warm — chestnut, mahogany or coffee-toned — and it forms a second, coloured highlight a short distance from the white surface sheen. In ordinary indoor light the coloured component is too weak to notice and the hair reads nearly black; in sunlight, where far more light is available, the warm interior colour becomes visible.
Light and shine: The contrast between a near-black overall appearance and warm glints in the sun is the defining feature; warm lamps strengthen the glints, cool daylight or overcast skies suppress them.
Sources: MedlinePlus Genetics: Is hair color determined by genetics?; Human hair color; Light Scattering from Human Hair Fibers (Marschner, Jensen, Cammarano, Worley & Hanrahan, SIGGRAPH 2003)