CMD of the starting sample (grey points) and the S_NYMG sample (coloured scale indicating the density of points). The solid lines indicate the limits of the MS and PMS locus, the black dashed curves show the isochrones from Phillips et al. (2020), Baraffe et al. (2015), and Marigo et al. (2017) stellar evolutionary models for 10 Myr, 30 Myr, 100 Myr, and 1 Gyr. The horizontal black dash-dotted lines indicate the M_G values corresponding to the turn-on (see Sect. 3.5) for the labelled masses. The red, orange, and blue dashed lines indicate the 0.1, 0.2, and 0.3 Μ_⊙ evolutionary tracks, respectively. The red arrow indicates twice the extinction vector for an M4 dwarf star with A_V = 0.22 mag.