Metallicities determined from the catalogues ARC, ZGR and FS of the open cluster NGC 3532 as a function of Gaia G_BP − G_RP colour. Empty circles show the estimates that were discarded after the respective cuts, whereas filled circles show the values that satisfied the cuts’ criteria. The black line and the shaded area show the [Fe/H] and σ[Fe/H] determined with high-resolution spectroscopy by Netopil et al. (2016) and used by B19, whereas the points with error bars show the weighted mean [Fe/H] and its dispersion of the respective catalogue. The percentage indicates the fraction of the stars that were accepted and used for [Fe/H] determination after the respective cuts.