Color developer for diffusion transfer

A process of producing a photographic image in a diffusion transfer photographic element, said photographic element comprising at least one supported light sensitive silver halide emulsion layer and a dispersion of a lipophilic color former in a high boiling photographically inert oil incorporated into, or in a layer adjacent, each said silver halide emulsion layer, which comprises developing said photographic element, after image-wise exposure to actinic radiation, in an alkaline medium of a pH below 12.5 in the presence of a color developer capable of developing silver halide and having the general formula:

• ##STR12## where R.sub.1 is COOM or SO.sub.3 M,
• M is H or a cation,
• R.sub.2 and R.sub.3 are H, lower alkyl or lower alkanoyl, unsubstituted or substituted by COOM or SO.sub.3 M, with at least one of R.sub.2 and R.sub.3 being other than H, or R.sub.2 and R.sub.3 taken together represent the atoms necessary to form a saturated heterocyclic ring with the nitrogen atom to which they are attached, and R.sub.4 is hydrogen, lower alkyl or lower alkoxy, said lipophilic color former being fast to diffusion at said pH and being reactive with oxidized color developer formed during development to form a coupled product that is diffusible at said pH, and allowing the coupled product to diffuse to an image receiving means for immobilizing said coupled product.