This collaborative study was conducted to determine the total monomeric anthocyanin concentration by the pH differential method, which is a rapid and simple spectrophotometric method based on the anthocyanin structural transformation that occurs with a change in pH (colored at pH 1.0 and colorless at pH 4.5). Eleven collaborators representing commercial laboratories, academic institutions, and government laboratories participated. Seven Youden pair materials representing fruit juices, beverages, natural colorants, and wines were tested. The repeatability relative standard deviation (RSD_r) varied from 1.06 to 4.16%. The reproducibility relative standard deviation (RSD_R) ranged from 2.69 to 10.12%. The HorRat values were ≤1.33 for all materials. The Study Director recommends that the method be adopted Official First Action.