Density maps of the G amplitude proxy versus G magnitude (left panels) and versus G_BP − G_RP colour (right panels) for Datasets A (top panels) B (middle panels) and C (bottom panels). The colours of each grid cell in the maps are related to the logarithm of the density of points in the cells according to the colour scale shown on the right of each row of panels. The two panels in a given row share the same density colour scale. We note that the top-right panel of Dataset A should be analysed with caution, as it contains sources with unreliable G_BP and/or G_RP.