Left panel: Hertzsprung-Russell diagram of M_G versus G_BP−G_RP for the 1194 lens stars in the final sample of source-lens pairs from Sect. 4.2.8. The continuous black line joining (−1, 5) and (5, 25) mag separates white dwarf stars from main sequence dwarfs/subdwarfs (Kilic et al. 2018). The lens masses are indicated by the colour of the plot points (see the scale at the bottom of the panel). The 55 lenses that are present in 58 of the source-lens pairs that do not have G_BP or G_RP magnitudes in GDR2 are plotted with black points at fixed colour G_BP−G_RP = −0.3 mag and using their computed absolute magnitudes M_G. Right panel: same as the left-hand panel for the 64 lens stars in the 76 microlensing events found in Sect. 5.2, except that the only lens that does not have a G_BP or G_RP magnitude is plotted in colour to indicate its estimated mass using photometry from external catalogues. The points from the left-hand panel are plotted in the background in light grey.