Same as Fig. 7, but now with different populations selected by the magnitude and color cuts defined in the main text highlighted. The green, red, blue, and magenta symbols correspond to populations number 1 (YSOs), 2 (carbon stars), 3 (RSG and OAGB stars), and 4 (B stars with 24 μm emission), respectively. Most of the stars in population 1, sources with strong 8.0 μm excess, have only very faint optical counterparts. Sources in population 2, which splits off the bright end of the MIR main sequence, are clearly identified with the branch of carbon stars.