IRAC colour–colour diagram for the entire IRAC sample (plotted as a surface grey map) and for the cross-correlation sample: blue circles and red triangles represent IR power-law and IR non-power-law galaxies according to Donley et al. (2012), respectively. The filled and empty symbols denote absorbed and unabsorbed sources, respectively. The symbols change in size to denote different ranges of X-ray luminosity. The solid line shows the revised IRAC-criteria wedge by Donley et al. (2012).