Also described as: ginger hair, copper hair
A warm range from deep auburn-brown to vivid copper-red.
typical range
An illustrative approximation, not a fixed definition.
Strongly warm by definition.
Depth and vividness vary considerably, from muted auburn to bright copper.
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.
Red hair is rich in pheomelanin, the red-yellow form of melanin, and usually low in eumelanin. Pheomelanin absorbs blue and green strongly and passes red and orange, so light returned from inside the fibre is intensely warm. Auburn adds a larger share of brown eumelanin, which darkens and deepens the red. Because the colour is highly saturated and concentrated at long wavelengths, it depends heavily on how much red light the source contains: some white LEDs render saturated reds poorly, so red hair can look browner under them than in daylight or incandescent light.
Light and shine: Red hair's internal highlight is strongly coloured, so shine reads as copper or gold rather than white; this also makes red hair one of the shades cameras most often oversaturate.
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)