Display colour conversion based on grey scale region

A method for driving an organic light emitting diode (OLED) display device, with intersecting data and gate lines, comprises: converting first digital image data including a plurality of colour digital data into any one of: second digital image data including the plurality of colour digital data and first white digital data, and third digital image data including a plurality of colour conversion digital data that converts the plurality of colour digital data and second white digital data, according to whether the first digital image data is included in a first greyscale region or a second greyscale region higher (e.g. above a greyscale level threshold) than the first greyscale region; second digital image data is converted into data voltages, supplied to display data lines, and synchronised gate pulses are sequentially supplied to the gate lines. Thus, colour temperature is uniformly maintained in all gray scale levels, reducing power consumption. A minimum, average or median value of colour digital data of the first image data, or luminance, may be calculated as a representative value.