Colour distribution of the GCs as function of radius. The moving window contains 105 GCs, and the data points show the independent bins. The number of components to fit was determined by the mclust software. The “error-bars” give the widths of the respective distributions. The thick solid line shows the colour of the combined light of GCs within the sliding window. The vertical dashed line at  ( ≃ 13 kpc) indicates the galactocentric distance where the colour distribution becomes bimodal.