Spatial and CMD distributions of final M31 and M33 supergiant samples (see Sect. 3.1). The left-hand panels display the spatial and CMD distributions of the M31 sample stars, while the right-hand panels present those of the M33 sample stars. Filled blue and red symbols denote blue (including some yellow) and red supergiants with a 5p astrometric solution, respectively; open cyan and pink circles indicate blue and red supergiants with a 6p solution. The dashed magenta line in the CMD panels marks G_BP − G_RP = 2.6. Clearly, M31 contains a significantly larger population of extremely red supergiant stars compared to M33.