Provided is a method for producing a gardenia blue pigment resistant to discoloration which may occur in colored sugar-coated food or pharmaceutical products. The method for producing such a gardenia blue pigment comprises performing membrane separation using a membrane (for example, an ultrafiltration membrane) with a molecular weight cut-off of 3000 Da or larger for removal of low-molecular compounds from a solution resulting from β-glucosidase treatment of an iridoid glycoside (for example, geniposide etc.) in the presence of a protein hydrolysate (for example, a casein protein hydrolysate), the iridoid glycoside being obtainable by extraction from fruits of Gardenia jasminoides (Rubiaceae). Also provided is a sugar-coated food or pharmaceutical product (for example, a sugar-coated tablet, a sugar-coated chewing gum, etc.) having a sugar-coating layer colored with the gardenia blue pigment obtainable by the above-described method.
