1. A method of processing data representing pixel colour, the data for each pixel being arranged as a luminance component and colour difference components, wherein the method comprises: dividing the data into first and second data portions, the first data portion comprising the luminance components and the second data portion comprising the colour difference components; deriving first and second instructions from a combined instruction word; processing the first and second date portions in parallel using first and second parallel processors within a processor architecture, the first and second parallel processors operating according to the first and second instructions, respectively; and combining the processed first and second data portions to provide processed pixel colour data.