The present invention relates to azo dyes of formula (1) which are soluble in organic solvents, wherein R1 is —CN, —COOR5, —CONR6R7 or a heterocyclic ring, R2 is unsubstituted or substituted alkyl, unsubstituted or substituted aryl, —CF3, —COOR5, —CONR6R7 or —COR5, R3 is hydrogen, —SO3M, alkyl, alkoxy, alkylcarbonyl, —NO2 or halogen, R4 is substituted aryl, substituted heteroaryl or an aryl-N═N-aryl radical, wherein one or both of the aryl radicals in aryl-N═N-aryl is/are unsubstituted or substituted, or a radical heteroaryl-N═N-heteroaryl, wherein one or both of the heteroaryl radicals in heteroaryl-N═N-heteroaryl is/are unsubstituted or substituted, R5 is hydrogen, alkyl or unsubstituted or substituted aryl, R6 is hydrogen, alkyl or unsubstituted or substituted aryl, R7 is hydrogen, alkyl or unsubstituted or substituted aryl, M+ is a cation, n is a number 1, 2 or 3 and m is a number 1, 2 or 3, to a process for the preparation thereof and to the use thereof in the production of coloured plastics or polymeric colour particles, and as printing inks, printing dyes, coating compositions and wood stains.