Optical CMDs of the stars detected in the different bands of Spitzer for which optical counterparts were found in the OGLE II and the MCPS catalogs. The overlaid gray contours indicate density of sources. The assumed distance modulus is ﹩\mathrm{DM}\,=18.93﹩, and the photometry has been corrected by the foreground reddening and extinction toward the SMC [﹩A_{V}\sim 0.12﹩, ﹩E( V-I) \sim 0.09﹩]. The right side scale in the last panel corresponds to apparent magnitudes. The gray bars indicate the expected 10 σ detection thresholds for naked sources on the main sequence in the different Spitzer wave bands, given the IRAC point‐source sensitivities (see Table 1) and the known color corrections. The vector in the upper right corner of the first panel indicates the extinction correction for 1 mag of reddening, assuming ﹩A_{V}/ E( V-I) =1.85﹩ (Bouchet et al. 1985). The dashed gray line in the 5.8 and 8.0 μm panels is parallel to the extinction vector and indicates the boundary over which the density of detected sources drastically increases. No naked photospheres should be detectable in the MIPS data: detection at 24 and 70 μm requires extensive reprocessing of the photospheric radiation by dust. All of the sources in the 70 μm diagram are consistent with misidentifications (their distribution in the CMD plane is the same as for the 3.6 μm or 4.5 μm sources). The rightmost panel sketches the locii of the different branches with their identification: MS (main sequence), BL (blue‐loop, helium core burning stars), FG (foreground), RSG (red supergiants), OAGB (oxygen‐rich asymptotic giant branch), C* (carbon stars), RGB (red giant branch).