Distributions of ∇_g−x for galaxies in each of our colour/Sérsic index subsamples (see Sect. 2 for more details), normalised to unit integral. Each panel shows the distribution for a different pair of bands. The median of each distribution is indicated by a vertical dashed line. These median values, and their uncertainties, can be found in Table 1. A bimodality in colour gradients for high- and low-n galaxies can be seen in all wavebands.