Top left: Kiel diagrams of the APOGEE and GALAH catalogues. The groups of stars selected to assess the magnitude trend are shown in salmon and cyan (group A: dwarfs and turn-off stars) and red and blue (group B: giants). Top right: median residuals of the radial velocity (Gaia minus catalogue) as a function of grvs_mag magnitude for the four samples. Bottom left: radial velocity correction model (dashed line) over-plotted on the median residuals of the radial velocity of the APOGEE B sample (red curve). Bottom right: median residuals of the radial velocity as a function of grvs_mag magnitude after applying the radial velocity correction, with respect to the five reference catalogues APOGEE, GALAH, GES, LAMOST, and RAVE. The upper panel shows group B stars (giants), and the lower panel presents group A stars (dwarfs and turn-off stars). All curves are shifted vertically (see text) and therefore show relative trends. The 68.3% confidence interval on the measurements of the medians is represented as shaded areas.