Color–magnitude diagrams (CMDs) of Gaia M_G versus the reddening-free (M_BP − M_RP) color indices. In the left panel, stars from the Gaia Catalogue of Nearby Stars of Gaia Collaboration (2021c) are marked with gray dots. In addition, SPB and β Cephei, as well as fundamental and first overtone Cepeheid stars from DR3 are marked with green diamonds, pink dots, orange squares and blue crosses, respectively. The six ULA Cepheid candidates are marked with green plus orange triangles (in the right panel). The right panel is the same as the left panel, but with background stars shown in gray scale marked with the same symbols. Absolute magnitudes were calculated from the distances of Bailer-Jones et al. (2021). The reddening vectors are shown with a solid blue line.