Variation of the EPIC pn hardness ratio HR2 with g − i colour for all 2XMMi matches with extended sources in the entire SDSS catalogue only having a log (f_x/f_r) larger than  −0.5. Each histogram corresponds to a g − i colour bin of 0.5. Black; g − i = 0.25, red; 0.75, green; 1.25, blue; 1.75, magenta; 2.25. Errors on hardness ratios are below 0.3 in all cases. We only show identifications with an individual identification probability higher than 90%, g and i mag brighter than 22.2, errors on g − i less than 0.2. Histograms are normalised to the total number of sources in the colour bins shown in Table 8.