Upper left: 2MASS CCD of J − H vs. H − K_S. The RSGs population is clumping within the range of 0.35 ≲ J − H ≲ 1.0 and 0.05 ≲ H − K_S ≲ 0.45 (dotted lines), and is indistinguishable from the O-AGBs. Upper right: IRAC CCD of IRAC1–IRAC2 vs. IRAC2–IRAC3. The previously defined PAH emission region of IRAC1 − IRAC2 ≤ 0 and IRAC2 − IRAC3 ≥ 0.3 is shown as dashed lines (Yang et al. 2018). There are only about only about 4% (after correcting for the completeness) of RSG candidates that show PAH emission features. Bottom left: WISE CCD of WISE1–WISE2 vs. WISE2–WISE3. The horizontal dashed line indicates F_ν, WISE2 = F_ν, WISE3 (WISE2 − WISE3 = 1.84), for which there are only seven targets above it. Bottom right: optical-MIR color excesses of BP − RP vs. (G − IRAC4)/(BP − RP). RSG candidates (and O-AGBs), C-AGBs, and x-AGBs having lowest, moderate, and highest ratio of (G − IRAC4)/(BP − RP) at BP − RP ≥ 2.0 (vertical dashed line), respectively.