Radial colour distribution of the extracted sources in the field of the cluster 1eRASS J113751.5 + 072839, split into three radial bins with respect to the optical cluster centre: d_centre < 1′ (orange), 1′< d_centre < 3′ (purple), and d_centre > 3′ (black). The histograms show the colour distribution of the data, the curves depict the median fit of the obtained posterior distribution, while the shaded regions show its 1σ uncertainty. The best fitting parameter values are shown in Table 1.