Human hair color account for all possible shades of brown, blond, or red (for example, platinum blond versus dark blond/light brown), nor does it explain why hair color sometimes darkens as a person ages. Several gene pairs control the light versus dark hair color in a cumulative effect. A person's genotype for a multifactorial trait can interact with the environment to produce varying phenotypes (see quantitative trait locus). Natural hair color can be brown, blond, black, red, or white; all natural hair colors including grey, white and lightest blond, are shades of brown. The Fischer–Saller scale, named after Eugen Fischer and , is
Linguistic relativity and the color naming debate of concrete evidence for its existence. Saunders is also bothered by the overall de-contextualization of color terminology and the failure of universalists to address the limitations of their methodologies. She points out that: "Ordinary colour talk is used in a variety of ways – for flat coloured surfaces, surfaces of natural objects, patches of paintings, transparent objects, shining objects, the sky, flames, illumination, vapours, volumes, films and so on, all of which interact with overall situation, illumination, edges, textures, patternings and distances, making the concept of sameness of colour inherently indeterminate". John A. Lucy's criticisms of Berlin and Kay's theory