Gaia colour vs. absolute magnitude diagram. Known PMS (in red circles) and classical Be stars (in violet diamonds) with good astrometric solution and corrected from interstellar extinction are plotted. An extinction vector corresponding to A_G = 1 is shown at the bottom left of each plot. Black contours trace Gaia sources within 500 pc with good astrometric solution. Left: all known sources. Right: subset of sources with all the observables that are used for training. The very blue classical Be star is ω CMa and it probably has a spurious G_RP magnitude because of being brighter than the bright limit of Gaia DR2.