PROBLEM TO BE SOLVED: To prevent the discoloration of a dye due to light, in an oral composition including a cationic germicide such as a cetylpyridinium chloride.SOLUTION: The present invention provides a discoloration inhibitor used for an oral composition including a cationic germicide and a dye, the discoloration inhibitor comprising at least one selected from the group consisting of a phosphate compound having three or more phosphate groups in a molecule and salt thereof.