Grapheme-color synesthesia is a condition in which visual letters or characters induce a specific color sensation. It has been suggested that a range of linguistic properties influence synesthetic grapheme-color correspondence, but the influence of graphemic (orthographic) information is not well understood. In this experiment, synesthetes chose up to two synesthetic colors for each Japanese Kanji character. The results showed that characters that could be divided into right and left subcomponents (radicals) were associated with a higher number of synesthetic colors than characters that could not be divided. This tendency was stronger for projectors, who perceive colors visually in external space, than for associators, who perceive colors in their ‘minds eye’. The results of this study suggest that the graphemic information of Kanji characters affects the number of synesthetic colors, especially for projectors.