The present application provides a process for changing the colour of keratinic fibres, comprising the steps of (i) producing the ready-to-use composition immediately prior to application by combining a pulverulent colour-changing formulation (A) and a liquid oxidizing agent formulation (B) in a recloseable vessel and then mixing, the colour-changing formulation (A) comprising at least one colour-changing composition and at least one inorganic alkalizing agent, and the liquid oxidizing agent formulation (B) comprising, in a cosmetically acceptable carrier, at least one oxidizing agent and at least one nonionic surfactant of the formula (I), R
1 -O-[G]
p (I), (ii) distributing the ready-to-use composition on the fibres, (iii) leaving the composition on the fibres for a period of 1 to 60 min, (iv) and washing the remaining composition out of the fibres.