The synthesis and the application of new dyes is described. In particular said new dyes can be incorporated in non-migratory state in hydrophilic colloid layers of photographic materials wherefrom they can be rapidly removed after being quickly decolourised in alkaline aqueous liquids used in the processing of said materials. In photographic applications dyes of the general formula (I) are provided with at least one ionisable group which permits solubilisation in aqueous and/or alkaline medium. ##STR1## The meanings of the symbols are as defined in the claims and in the description.