Left: color−magnitude diagram for non-spurious X-ray sources in HM1 having reliable 2MASS counterparts. The dashed line corresponds to the main sequence shifted for a distance of 92 pc (that of HD 156301), the solid and dotted lines correspond to the main sequences for a DM = 12.6 mag, typical of the cluster (Vázquez & Baume 2001), without and with correction for the cluster’s absorption (E(B − V) = 1.84   mag,R_V = 3.3, see Vázquez & Baume 2001), respectively. The main sequence magnitudes and colors are taken from Martins & Plez (2006) for O-stars (masses  >15 M_⊙) and Tokunaga (2000) for the other spectral types (masses in the range 0.1−15 M_⊙). The reddening vector corresponds to the reddening expected for the cluster. Middle: the same color−magnitude diagram with Siess et al. (2000) isochrones, for DM = 12.6 mag and E(B − V) = 1.84 mag, superimposed as dashed lines. The displayed tracks correspond to masses in the range 0.1−7.0 M_⊙ (spectral types M6 to B3). Right: color−color diagram for the same objects. The dotted line shows the intrinsic (i.e., dereddened) colors of classical T Tauri stars (Meyer et al. 1997), the dashed lines correspond to increasing values of absorption (using R_V = 3.3 and Cardelli et al. 1989 extinction law) for the blue and red limits of the main sequence for low-mass stars and of the TTs sequence. Note that for these figures the 2MASS JHK photometry was transformed into the Bessel & Brett system (see http://www.astro.caltech.edu/~jmc/2mass/v3/transformations/). The color version of this figure is available online.