Data is presented on the colour and spectral reflectances of stool samples from healthy young infants (mean age 6 days). The range of spectral reflectances is well described by a pigment mixture model with three componentsa pale component corresponding to partially digested milk fats, a yellow component corresponding to bilirubin breakdown products, and a dark component corresponding to meconium and bilirubin. Most stools were tan, beige or olive but white, grey and light grey were also observed. (c) 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 585-591, 2015