Precision and accuracy validation of [Fe/H]_SSPP for M 13 member stars. Lower left panel: proper-motion-cleaned CMD in the GaiaG, G_BP, and G_RP passbands. For reference to the lower right panel, G_BP − G_RP is additionally indicated by colored symbols. Right panels: marginalized distribution of deviations (top) and behavior with evolutionary state (bottom) of SSPP metallicities with respect to the literature value: [Fe/H]_M 13 = −1.53 dex. Red points and error bars denote the means and standard deviations in bins of 1 mag width in G, whereas underlying gray bars represent the median of the SSPP uncertainties on [Fe/H].