Although hair color can be perceived as a continuum (as seen in Fig. 1), it can be divided into categories or clusters based on spectrophotometric measurements in the CIE L*a*b* color space and these clusters can be well discriminated from each other. The discrepancies between self-reported hair color and observer-reported hair color and the poor separation of observer-reported color groups compared to those defined by clustering analysis emphasize the importance for objective measurement of individuals to be included in research studies. For repeatability and validityAmerican Journal of Physical Anthropology
of studies, phenotypes must be defined as well as possible and the objective measurement methods and analysis strategies presented here may be of assistance
Hair color measurement and variation
Michelle Vaughn et al.
Pigmentation of hair in humans has been investigated by medical scientists, anthropologists and, more recently, by forensic scientists. In every investigation, hair color must first be defined by the researchers. Subjective color assessment inhibits the reproducibility of experiments and the direct comparison of results. The aim of this study was to objectively measure human hair color and examine the variation found in a population with European ancestry, using the CIE L*a*b* color space. Observer-perceived hair colors were compared with self-reported hair colors and the color as measured by reflective spectrophotometry of 132 subjects of European ancestry. The presented data show that self-reported hair colors and observer-reported colors are similar; however, these categories are not necessarily the best way to categorize hair color for quantitative research. Using a two-step cluster analysis, hair color can be divided into categories or clusters based on spectrophotometric measurements in the CIE L*a*b* color space and these clusters can be well discriminated from each other. This separation is primarily based on the b* (yellow) color component and the clusters show agreement to observer-reported colors. This study illustrates the possibilities for and necessity of objectively defining the hair color phenotype for various downstream applications.