Colours of GSP-Spec solar-analogue candidates as a function of GSP-Phot extinction estimates. W₁ and W₂ denote AllWISE photometry (Cutri et al. 2021). We restrict the comparison to candidates with W₁ > 8 mag, because AllWISE photometry suffers from saturation for brighter sources. Panel c: the red line is a linear increase with abp_gspphot offset by the mean G_BP − W₂ colour of 589 stars where A₀ < 0.001 mag according to GSP-Phot. The red interval marks the uncertainty from the standard deviation of the mean. The quoted root-mean-square (RMS) difference is between the G_BP − W₂ colour and abp_gspphot plus the mean.