The stool color card for the early detection of biliary atresia has been developed using multispectral images of stools of newborns. The color and its reflectance were measured and analyzed spectrally and used to design the stool color card. The representative texture was selected by medical specialists from color images reproduced using six-band images. The spectral reflectance of the images was replaced and edited in accordance with the result of spectral and chromaticity analysis. Since 2021, the stool color card has been included in the Maternal and Child Health Handbook that is distributed to all pregnant women by their respective local government in accordance with the Maternal and Child Health Law in Japan.