1. A color display comprising: a plurality of composite pixels, each composite pixel comprising sub-pixels of more than one color type; wherein sub-pixels of at least one of the color types are provided with differing luminance capability in different composite pixels; and further comprising an image data processing unit (IDPU), and the IDPU is configured to: receive input image data of a standard format; modify the input image data into output image data to account for a discrepancy between the luminance capability of each sub-pixel and a luminance capability for each sub-pixel as expected based on the input image data; and output the output image data to control the plurality of the composite pixels; wherein the IDPU is configured to modify the input image data by: processing groups of pixels in the input image data corresponding to the smallest repeating unit of the pixel pattern of the display together; matching the pattern pixel luminances in the group specified by the input image data to the closest of a set of zero effective resolution loss patterns; and transferring luminance between sub-pixels to account for the luminance discrepancy in a manner informed by the result of the pattern matching.