An adhesive and a pressure-sensitive transfer adhesive tape formed by coating the adhesive on a base material are provided. The adhesive has a color when applied to a substrate and, after application can be decolored. The adhesive comprises a colored material colored by reacting a leuco dye with a developer, a material (decoloring material) having a decoloring effect by acting on the colored material, and microcapsules including a material allowing both of the colored and decoloring materials to react by acting on at least one of them.