colour distribution of galaxies in the JKCS 041 direction (points) and in a control region all around the cluster, normalized to the cluster solid angle (lower, black, curve). The (blue) curve with shaded 68% (highest posterior credible) intervals is a Gaussian fit to the data. Approximated (i.e. ) error bars are shown for display purpose only. The dashed blue Gaussian lines show the colour spread expected for a 250 Myr (central panel) or 50 Myr (right panel) age spread.