A single-part colour developing concentrate with a pH greater than or equal to 7 which contains at least 0.02 mol of a colour developer substance and at least 0.015 mol of an antioxidant per litre, characterised in that the concentrate contains 0.05 to 35 g per litre of a wetting agent soluble in water in this amount, is distinguished by very good stability in storage at low temperatures and the discharge behaviour from the concentrate bottle is considerably improved and soiling of the processing equipment is avoided. Furthermore, the optical brightener precipitation occurring in practice in the bleach fixing bath is also prevented.