Comparisons between sample fgkm_1 and intermediate samples based on some of the criteria used to define sample fgkm_2. Top panel: illustrates the distance–parallax–error constraint and the lower panel shows the (G − G_RP)₀ − (G_BP − G_RP)₀ relation after imposing the colour–T_eff and colour–colour cuts described in Sect. 4.2. In both panels, the sources in fgkm_1 are shown in the background, while those satisfying the criteria are illustrated in the foreground, colour-coded according to logarithmic count.