Central colour magnitude relation: age colour measured at 1.̋5 (upper panel) and metallicity colour measured at 1.̋5 (lower panel) are plotted against the absolute r-band magnitude. Error bars denote the uncertainties of the isophotal colours. Galaxies are coloured based on their g − r gradient groups (see Fig. 4). The black line describes the running mean of the colour within a 1 mag interval and the grey shaded area displays the corresponding standard deviation of the galaxies.