Top panel: accreted mass fraction as a function the projected distance from the cluster centre, normalised to the virial radius of the cluster (R_vir = 0.7 Mpc, Drinkwater et al. 2001). Red dots indicate galaxies in the high-density region of the cluster, while blue dots indicate galaxies in the low-density region. The vertical grey region shows the range of cluster-centric distance where a clear separation occurs: galaxies located inside ∼0.8–1 degree from the core of the cluster show a higher outer envelope mass fraction. Bottom panel: accreted mass fraction as a function of the (g − i) average colour for galaxies in the low- (blues dots) and high- (red dots) density regions of the cluster. On average, redder galaxies have higher accreted mass fractions. FCC 277 is in the transition region from high-to-low density; this region has a higher accreted mass fraction, but has colours comparable with galaxies in the low-density region.