This invention relates to a method of co-dispensing a hair dye composition under pressure wherein there is provided a first container containing a hair dye and propellant material and a second container disposed within the first container containing a hair dye developer material. The second container is provided with a flexible wall against which the propellant acts. A discharge passageway is defined via a nozzle structure and passage of the materials through the nozzle is controlled via a valve structure having first and second valves. The first valve permits control of the flow of material between a first orifice communicating with the first container, a second orifice communicating with the second container and the discharge passageway. The second valve permits control of the flow of material through the second orifice only. The first and second valves are connected for concurrent operation thereof, such that moving the nozzle structure operates the first and second valves to permit simultaneous flow of the materials from the first and second containers through the passageway under the influence of the propellant at an overall flow rate not greater than about 1.8 gm/sec.