Colour–colour diagrams showing the evolution of galaxies in NUV-u vs. u-r space as they interact with different clusters. The top panel is for model galaxy G1, and the bottom panel for G2. The colour is indicating different environments as shown in the legend. Stars mark simulation times with their brightness encoding 0, 0.5, 1.5 and 2 h^-1 Gyr (the brightness corresponds to the one used for the big squares in Figs. 9a and b). The grey shaded contours represent the densities of the observed early- (upper right concentration) and late-type (lower left peak) galaxy populations, as determined by Schawinski et al. (2014).