Colour-magnitude diagrams of Melotte 22 and NGC 2682 as examples of the clusters with [Fe/H] in the literature. The filled grey circles are high-quality member stars from Cantat-Gaudin et al. (2020), and open circles are all matched stars with LAMOST RV measurements. Right panel: stars good for the cluster V_rad determination (FLAG=1) are colour-coded with their RV values. Left panel: the colour-filled dots are stars good for [Fe/H] determination (FLAG=12), and the black dots are stars without [Fe/H] determination or with discarded [Fe/H]. The dashed curve in each sub-figure is the PARSEC isochrone with the Cantat-Gaudin et al. (2020) cluster parameters.