A process for producing dichlorodiketopyrrolopyrrole pigment of the .alpha. modification, which comprises wet milling crude dichlorodiketopyrrolopyrrole pigment wherein an .alpha. modification and a .beta. modification coexist in the presence of a milling agent and a wetting agent, dichlorodiketopyrrolopyrrole pigment of the .alpha. modification obtained the process and a color composition which contains the pigment and a pigment carrier.